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COLEGIO DE DAGUPANArellano Street, Dagupan City 2400, Pangasinan

DEPARTMENT OF MATHEMATICS AND NATURAL SCIENCES

Biological Science

First Semester, Academic Year 2013 – 2014

Life is dened as

1! A distincti"e c#aracteristic o$ a li"ing  organism $rom dead organism  ornon%li"ing t#ing, as speci&cally distinguis#ed 'y t#e capacity to gro(,meta'oli)e, respond to stimuli!, adapt, and reproduce 

2! *#e 'iota o$ a particular region 

 *#e 'asic c#aracteristics o$ a li"ing t#ing are as $ollo(s+

• (it# an organi)ed structure per$orming a speci&c $unction

• (it# an a'ility to sustain eistence, e-g- 'y nouris#ment

• (it# an a'ility to respond to stimuli or to its en"ironment

• capa'le o$ adapting

• (it# an a'ility to germinate or reproduce

.i$e on eart# 'egan more t#an 3 'illion years ago, e"ol"ing $rom t#e most'asic o$ micro'es into a da))ling array o$ compleity o"er time- /ut #o( didt#e &rst organisms on t#e only no(n #ome to li$e in t#e uni"erse de"elop$rom t#e primordial soup

ere are sciences t#eories on t#e origins o$ li$e on art#-

!" Scien#ic E$ol%#ion

 *#is t#eory relies strongly on t#e /ig /ang t#eory o$ t#e Creation o$ t#e5ni"erse, (#ic# (as t#e 'eginning o$ t#e $ormation o$ matter- *#ise"entually led to t#e creation o$ planets and li$e on eart# as it e"ol"edo"er millions o$ years in a natural en"ironment conduci"e $or c#emicalreactions- 6e #a"e seen $airly comple 'ioc#emicals spontaneously$orm in simple simulations o$ eart#ly pre'iotic conditions, suc# as int#e 5rey78iller eperiments yielding amino acids- Amino acids $orm in

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a (ide "ariety o$ conditions- 8any o$ t#e steps $rom inorganic matterto sel$ replicating li$e $orms remain a mystery to us, 'ut muc# o$ t#eun$olding o$ t#e story a$ter t#e de"elopment o$ multicellular organismsmeta)oans! is $ound in eart#s geologic $ossil record and in D9Agenetic se:uences-

&" S'ecial C(ea#ion

According to t#is t#eory, all t#e di;erent $orms o$ li$e t#at occur todayon planet eart# #a"e 'een created 'y <od, t#e almig#ty- *#is idea is$ound in t#e ancient scriptures o$ almost e"ery religion- According toindu myt#ology, .ord /ra#ma, t#e <od o$ Creation, created t#e li"ing(orld in accordance to #is (is#- According to t#e C#ristian 'elie$, <odcreated t#is uni"erse, plants, animals and #uman 'eings in a'out sinatural days- *#e Si# myt#ology says t#at all $orms o$ li$e including#uman 'eings came into 'eing (it# a single (ord o$ <od- Special

creation t#eory 'elie"es t#at t#e t#ings #a"e not undergone anysigni&cant c#ange since t#eir creation- Creationists generally 'elie"et#e /i'les eplanation t#at <od created a num'er o$ 'asic groups o$ animals and plants as descri'ed in t#e &rst part o$ <enesis- *#ey'elie"e t#at (#ile <od created eac# group (it# t#e possi'ility o$ agood deal o$ "ariation, t#ey 'roug#t $ort# according to t#eir o(n ind-/y de&nition, t#e $ait#%'ased *#eory o$ Special Creation is purely areligious concept, accepta'le only on t#e 'asis o$ $ait#- =t #as noscienti&c 'asis-

)" Biogenesis

 *#e 'elie$ t#at li"ing t#ings come only $rom ot#er li"ing t#ings e-g- aspider lays eggs, (#ic# de"elop into spiders!- =t may also re$er to'ioc#emical processes o$ production in li"ing organisms- *#e .a( o$ /iogenesis, attri'uted to .ouis Pasteur, states t#at li$e arises $rom pre%eisting li$e, not $rom nonli"ing material- Pasteurs and ot#ers!empirical results (ere summari)ed in t#e p#rase Omne vivum ex vivo,.atin $or "all life [is] from life", also no(n as t#e >la( o$ 'iogenesis>-Pasteur stated+ >La génération spontanée est une chimère>>Spontaneous generation is a dream>!-

*" A+iogenesis

=n t#e natural sciences, abiogenesis  % also no(n as spontaneousgeneration % is t#e study o$ #o( li$e on art# could #a"e arisen $rominanimate matter- *#is is also re$erred to as t#e >primordial soup>t#eory o$ e"olution li$e 'egan in (ater as a result o$ t#e com'inationo$ c#emicals $rom t#e atmosp#ere and some $orm o$ energy to maeamino acids, t#e 'uilding 'locs o$ proteins, (#ic# (ould t#en e"ol"e

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into all t#e species!- =t s#ould not 'e con$used (it# e"olution, (#ic# ist#e study o$ #o( groups o$ already li"ing t#ings c#ange o"er time-8ost amino acids, o$ten called >t#e 'uilding 'locs o$ li$e>, can $orm "ianatural c#emical reactions unrelated to li$e, as demonstrated in t#e8iller%5rey eperiment and similar eperiments, (#ic# in"ol"ed

simulating t#e conditions o$ t#e early art#- =n all li"ing t#ings, t#eseamino acids are organi)ed into proteins, and t#e construction o$ t#eseproteins is mediated 'y nucleic acids- *#is o$ t#ese organic molecules&rst arose and #o( t#ey $ormed t#e &rst li$e is t#e $ocus o$ a'iogenesis- gyptians 'elie"ed t#at mud o$ t#e 9ile ?i"er couldspontaneously gi"e rise to many $orms o$ li$e- *#e idea o$ spontaneousgeneration (as popular almost till se"enteent# century- 8anyscientists lie Descartes, <alileo and elmont supported t#is idea-

," T-eo(. of C-e/ical E$ol%#ion

 *#is t#eory is also no(n as 8aterialistic *#eory or P#ysico%c#emical *#eory- According t#is t#eory, t#e origin o$ li$e on eart# is t#e result o$ a slo( and gradual process o$ c#emical e"olution t#at pro'a'lyoccurred a'out 3-@ 'illion years ago- *#is t#eory (as proposedindependently 'y t(o scientists % A-=-parin, a ?ussian scientist in 1B23and -/-S aldane, an nglis# scientist, in 1B2@-

0" T-eo(. of Ca#as#(o'-is/

 *#is t#eory on t#e origin o$ li$e is simply a modi&cation o$ t#e t#eory o$ Special Creation- =t states t#at t#ere #a"e 'een se"eral creations o$ li$e

'y <od, eac# preceded 'y a catastrop#e resulting $rom some ind o$ geological distur'ance- According to t#is t#eory, since eac#catastrop#e completely destroyed t#e eisting li$e, eac# ne( creationconsisted o$ li$e $orm di;erent $rom t#at o$ pre"ious ones- Frenc#scientists <eorges Cu"ier 1EB%1@32! and r'igney 1@02 to 1@3!(ere t#e main supporters o$ t#is t#eory-

1" Ino(ganic Inc%+a#ion

Proposed 'y Pro$essor 6illiam 8artin, o$ Dsseldor$ 5ni"ersity, andPro$essor 8ic#ael ?ussell, o$ t#e Scottis# n"ironmental ?esearc#

Centre in <lasgo(, t#is t#eory states t#at =nstead o$ t#e 'uilding 'locso$ li$e $orming &rst, and t#en $orming a cell%lie structure, t#eresearc#ers say t#e cell came &rst and (as later &lled (it# li"ingmolecules- *#ey say t#at t#e &rst cells (ere not li"ing cells 'utinorganic ones made o$ iron sul&de and (ere $ormed not at t#e art#ssur$ace 'ut in total darness at t#e 'ottom o$ t#e oceans- *#e t#eorypostulates t#at li$e is a c#emical conse:uence o$ con"ection currentst#roug# t#e art#s crust and, in principle, could #appen on any (et,

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rocy planet-

2" Endos./+io#ic T-eo(.

 *#is t#eory, espoused 'y .ynn 8argulis, suggests t#at multiple $orms

o$ 'acteria entered into sym'iotic relations#ip to $orm t#e euaryoticcell- *#e #ori)ontal trans$er o$ genetic material 'et(een 'acteriapromotes suc# sym'iotic relations#ips, and t#us many separateorganisms may #a"e contri'uted to 'uilding (#at #as 'een recogni)edas t#e .ast 5ni"ersal Common Ancestor .5CA! o$ modern organisms- ames .o"elocs <aia t#eory, proposes t#at suc# 'acterial sym'iosisesta'lis#es t#e en"ironment as a system produced 'y and supporti"eo$ li$e- is arguments strongly (eaen t#e case $or li$e #a"ing e"ol"edelse(#ere in t#e solar system-

3" Pans'e(/ia 4 Cells F(o/ O%#e( S'ace

Some scientists 'elie"e t#at t#e simplest li$e%$orms, (#ole cellsespecially micro'ial cells!, #a"e 'een transported to t#e art# $rometraterrestrial sources- =n t#is (ay, a process called panspermiameans seeds e"ery(#ere! mig#t #a"e initiated li$e on art#- 8ostmainstream scientists #a"e not supported panspermia, 'ut earlyc#allenges #a"e 'een t#(arted in recent years due to disco"eries suc#as terrestrial micro'es t#at sur"i"e in etreme en"ironments andincredi'ly aged yet "ia'le microorganisms $ound in ancient rocs- =naddition, (ater essential $or li$e! #as 'een disco"ered on ot#er planetsand moons, and organic c#emicals #a"e 'een $ound on meteorites and

in interstellar de'ris-

!5" Cos/ogon.

Cosmogony is any t#eory concerning t#e coming into eistence ororigin o$ t#e uni"erse, or a'out #o( reality came to 'e- =n t#especiali)ed contet o$ space science and astronomy, t#e term re$ers tot#eories o$ creation o$ t#e Solar System- For eample, <ree myt#ologyand some religions o$ t#e Ancient 9ear ast re$er to c#aos, t#e$ormless or "oid state o$ primordial matter preceding t#e creation o$ t#e uni"erse or cosmos in creation myt#s- Cosmogony can 'e

distinguis#ed $rom cosmology, (#ic# studies t#e uni"erse at large andt#roug#out its eistence, yet does not in:uire directly into t#e sourceo$ li$e or its origins-

!!" Ma(ine T-eo(.

 *#e 8arine *#eory suggests t#at li$e may #a"e 'egun at t#esu'marine #ydrot#ermal "entsG t#eir rocy noos could t#en #a"e

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concentrated t#ese molecules toget#er and pro"ided mineral catalysts$or critical reactions- "en no(, t#ese "ents are ric# in c#emical andt#ermal energy t#at sustains "i'rant ecosystems-

!&" Elec#(ic S'a(6 T-eo(.

lectric spars can generate amino acids and sugars $rom anatmosp#ere loaded (it# (ater, met#ane, ammonia and #ydrogen, as(as s#o(n in t#e $amous 8iller%5rey eperiment reported in 1BH3,suggesting t#at lig#tning mig#t #a"e #elped create t#e ey 'uilding'locs o$ li$e on art# in its early days- "er millions o$ years, largerand more comple molecules could $orm- Alt#oug# researc# since t#en#as re"ealed t#e early atmosp#ere o$ art# (as actually #ydrogen%poor, scientists #a"e suggested t#at "olcanic clouds in t#e earlyatmosp#ere mig#t #a"e #eld met#ane, ammonia and #ydrogen and'een &lled (it# lig#tning as (ell-

!)" T(i+al and M.#-ological

 *#oug# not strictly scienti&c $rom our modern de&nition, ancient lore(as 'elie"ed to 'e a scienti&c 'elie$ in t#eir day, as it attempted toeplain (#at (as o'ser"ed- From t#e tri'es o$ ancient times to t#emyt#ologies o$ more modern cultures, t#ere are countless stories o$ #o( li$e 'egan- Some are 'ased in pagan 'elie$s, (#ile ot#ers are'ased on creation resulting $rom a #oly deity- *#is collection o$ myt#s,legend and tri'al no(ledge #anded do(n o"er generations is t#ecollecti"e epression o$ #o( man attempts to eplain #is (orld and #is

place in it-

Di7e(ence +e#8een Ani/als and Plan#s

 *#e di;erence 'et(een plant and animal comes do(n to cell structure-Plants #a"e a toug#, cellulose (all and animals donIt- Plants #a"ec#loroplasts t#at p#otosynt#esi)e matter $rom car'on dioide and sun- Also,plants tae in car'on dioide to #elp create plant material and gi"e o; oygen as a 'yproduct, (#ereas animals tae in oygen and gi"e o; car'on

dioide as a 'yproduct- Plants use t#e energy $rom t#e sun to con"ertatmosp#eric car'on dioide into simple sugar to 'uild its 'ody- .astly, mostplant cells and some animal cells #a"e a "acuoleG an organelle responsi'le$or remo"ing and storing (aste, eeping t#e cell $rom collapsing in uponitsel$, and maintaining pG acid7'ase 'alance-

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Animals are a'le to mo"e, (#ile plants remain stationary- Animals also#a"e a comple ner"ous system t#at can per$orm many tass, (#ile plantslac a 'rain and all t#e organs t#at animals #a"e to carry out meta'olic$unction as animals tae t#eir car'on $rom organic su'stances and plantstae t#eir car'on $rom t#e air- Animals #a"e a &ed gro(t#, (#ereas mostplants can gro( inde&nitely, 'ranc#ing out in many directions-

P(o#o'las/9 #-e li$ing 'a(# of #-e cell:

P(o#o'las/  is t#e li"ing contents o$ a cell  t#at is surrounded 'y aplasma mem'rane- =t is a general term $or t#e cytoplasm- Protoplasm iscomposed o$ a miture o$ small molecules suc# as ions, amino acids,monosacc#arides  and (ater, and macromolecules  suc# as nucleic acids,proteins, lipids  and polysacc#arides- =n euaryotes  t#e protoplasm

surrounding t#e cell nucleus is no(n as t#e cytoplasm and t#at inside t#enucleus as t#e nucleoplasm- =n proaryotes t#e material inside t#e plasmamem'rane is t#e 'acterial cytoplasm, (#ile in <ram%negati"e 'acteria  t#eregion outside t#e plasma mem'rane 'ut inside t#e outer mem'rane is t#eperiplasm-

 *#e (ord >protoplasm> comes $rom t#e <ree  protos  $or rst , and plasma  $or thing formed- =t (as &rst used in 1@4E 'y ugo "on 8o#l  todescri'e t#e >toug#, slimy, granular, semi%Juid> su'stance (it#in plant cells,to distinguis# t#is $rom t#e cell (all, cell nucleus and t#e cell sap (it#in t#e

"acuole- *#omas uley later re$erred to it as t#e >p#ysical 'asis o$ li$e> andconsidered t#at t#e property o$ li$e resulted $rom t#e distri'ution o$ molecules (it#in t#is su'stance- =ts composition, #o(e"er, (as mysteriousand t#ere (as muc# contro"ersy o"er (#at sort o$ su'stance it (as-Attempts to in"estigate t#e origin o$ li$e t#roug# t#e creation o$ synt#etic>protoplasm> in t#e la'oratory (ere not success$ul-

 *#e idea t#at protoplasm o$ euaryotes is di"isi'le into a groundsu'stance called >cytoplasm> and a structural 'ody called t#e cell nucleusreJects t#e more primiti"e no(ledge o$ cell structure t#at preceded t#ede"elopment o$ electron microscopy, (#en it seemed t#at cytoplasm (as a#omogeneous Juid and t#e eistence o$ most su'%cellular compartments, or#o( cells maintain t#eir s#ape, (as unno(n- KEL *oday, it is no(n t#at t#ecell contents are structurally "ery comple and contain multiple organelles-

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Protoplasm can eist in t(o $orms+ a li:uid%lie sol state or a Melly%liegel state- 6#et#er protoplasm is in t#e sol or t#e gel state depends on t#ep#ysiological state o$ t#e cell-

P(o'e(#ies of a P(o#o'las/

a" P-.sical '(o'e(#ies of '(o#o'las/-

=t is a transparent and Melly%lie material, t#e consistency "arying $rom t#emore li:uid, slig#tly gelatinous (#ite o$ a $res# egg to t#at o$ semi%solidi&edgelatin o$ Melly- =$ t#e protoplasm is more li:uid it is termed a sol, i$ moregelatinous, a gel-

+" C-e/ical '(o'e(#ies of '(o#o'las/-

 *#e c#emical properties o$ protoplasm can 'e di"ided into inorganic andorganic su'stances-

o Ino(ganic S%+s#ances-

=norganic su'stances are (ater, (#ic# mae up B0N o$ t#e protoplasm,mineral salts, suc# as 9aCl%salt, and gases lie oygen and car'ondioide-

o O(ganic S%+s#ances" 

rganic su'stances include proteins, car'o#ydrates, lipids, nucleicacids and en)ymes-

F%nc#ions of #-e P(o#o'las/ 

o Re'(od%c#ion 

Cells di"ide to $orm identical daug#ter cellsG $unction o$ t#e nucleus o$ t#e protoplasm, e-g- t#e meristematic region o$ angiosperms-

o I((i#a+ili#. 

 *#e li"ing protoplasm responds to stimuli, e-g- retinal cells in t#e eyerespond to lig#t-

o C-e/ical

All t#ese $unctions are carried out inside t#e cell, e-g- respiration in t#emitoc#ondriaG

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o E;c(e#ion 

Cells must get rid o$ ecretory (astesG t#ey usually di;use out o$ t#ecell t#roug# t#e cell mem'rane-

o Mo$e/en# 

8o"ement is e#i'ited 'y certain cells, e-g- unicellsG t#e protoplasm o$ t#ese cells #as a contractile a'ility-

o G(o8#- 

<ro(t# $ollo(s on cell di"isionG t#ere is an assimilation o$ protoplasmand an increase in si)e-

THE CELL

 *#e cell  is t#e 'asic structural, $unctional and 'iological unit o$ allno(n li"ing organisms- =t is t#e smallest unit o$ li$e t#at is classi&ed as ali"ing t#ing ecept "irus, (#ic# consists only o$ D9A7?9A co"ered 'y proteinand lipids!, and is o$ten called t#e >'uilding 'loc o$ li$e>-

=t consists o$ a protoplasm  enclosed (it#in a mem'rane, (#ic#contains many 'iomolecules suc# as proteins and nucleic acids- rganismscan 'e classi&ed as unicellular consisting o$ a single cellG including most'acteria! or multicellular including plants and animals!-

6#ile t#e num'er o$ cells in plants and animals "aries $rom species tospecies, umans contain a'out 100 trillion 1014! cells- 8ost plant and animalcells are 'et(een 1 and 100 micrometres  and t#ere$ore are "isi'le onlyunder t#e microscope-

 *#e cell (as disco"ered 'y ?o'ert ooe in 1EEH- *#e cell t#eory, &rstde"eloped in 1@3B 'y 8att#ias ao' Sc#leiden and *#eodor Sc#(ann, states

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t#at all organisms are composed o$ one or more cells, t#at all cells come$rom preeisting cells, t#at "ital $unctions o$ an organism occur (it#in cells,and t#at all cells contain t#e #ereditary in$ormation necessary $or regulatingcell $unctions and $or transmitting in$ormation to t#e net generation o$ cells-Cells emerged on planet art# at least 4-0–4-3 'illion years ago-

 *#e (ord cell comes $rom t#e .atin cella, meaning >small room>- *#edescripti"e term $or t#e smallest li"ing 'iological structure (as coined 'y?o'ert ooe in a 'oo #e pu'lis#ed in 1EEH (#en #e compared t#e corcells #e sa( t#roug# #is microscope to t#e small rooms mons li"ed in-

  *#e cell t#eory, or cell doctrine, states t#at all organisms arecomposed o$ similar units o$ organi)ation, called cells- *#e concept (as$ormally articulated in 1@3B 'y Sc#leiden O Sc#(ann and #as remained as

t#e $oundation o$ modern 'iology- *#e idea predates ot#er great paradigmso$ 'iology including Dar(inIs t#eory o$ e"olution 1@HB!, 8endelIs la(s o$ in#eritance 1@EH!, and t#e esta'lis#ment o$ comparati"e'ioc#emistry1B40!-

Fi(s# Cells Seen in Co(6 

6#ile t#e in"ention o$ t#e telescope made t#e Cosmos accessi'le to#uman o'ser"ation, t#e microsope opened up smaller (orlds, s#o(ing (#atli"ing $orms (ere composed o$- *#e cell (as &rst disco"ered and named 'y

?o'ert ooe in 1EEH- e remared t#at it looed strangely similar to cellulaor small rooms (#ic# mons in#a'ited, t#us deri"ing t#e name- o(e"er(#at ooe actually sa( (as t#e dead cell (alls o$ plant cells cor! as itappeared under t#e microscope- ooeIs description o$ t#ese cells (aspu'lis#ed in Micrographia- *#e cell (alls o'ser"ed 'y ooe ga"e noindication o$ t#e nucleus and ot#er organelles $ound in most li"ing cells- *#e&rst man to (itness a li"e cell under a microscope (as Anton "an.eeu(en#oe, (#o in 1E4 descri'ed t#e algae Spirogyra- an .eeu(en#oepro'a'ly also sa( 'acteria-

Fo(/%la#ion of #-e Cell T-eo(.

=n 1@3@, *#eodor Sc#(ann and 8att#ias Sc#leiden (ere enMoying a$ter%dinner co;ee and taling a'out t#eir studies on cells- =t #as 'een suggestedt#at (#en Sc#(ann #eard Sc#leiden descri'e plant cells (it# nuclei, #e (asstruc 'y t#e similarity o$ t#ese plant cells to cells #e #ad o'ser"ed in animaltissues- *#e t(o scientists (ent immediately to Sc#(annIs la' to loo at #is

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slides- Sc#(ann pu'lis#ed #is 'oo on animal and plant cells Sc#(ann1@3B! t#e net year, a treatise de"oid o$ acno(ledgments o$ anyone elseIscontri'ution, including t#at o$ Sc#leiden 1@3@!- e summari)ed #iso'ser"ations into t#ree conclusions a'out cells+

1- *#e cell is t#e unit o$ structure, p#ysiology, and organi)ation in li"ingt#ings-

2- *#e cell retains a dual eistence as a distinct entity and a 'uilding'loc in t#e construction o$ organisms-

3- Cells $orm 'y $ree%cell $ormation, similar to t#e $ormation o$ crystalsspontaneous generation!-

6e no( today t#at t#e &rst t(o tenets are correct, 'ut t#e t#ird is clearly

(rong- *#e correct interpretation o$ cell $ormation 'y di"ision (as &nallypromoted 'y ot#ers and $ormally enunciated in ?udolp# irc#o(Is po(er$uldictum, Omnis cellula e cellula,+ QAll cells only arise $rom pre%eisting cellsR-

Mode(n Cell T-eo(.

1- All no(n li"ing t#ings are made up o$ cells-

2- *#e cell is structural O $unctional unit o$ all li"ing t#ings-

3- All cells come $rom pre%eisting cells 'y di"ision- Spontaneous

<eneration does not occur!-

4- Cells contains #ereditary in$ormation (#ic# is passed $rom cell to cellduring cell di"ision-

H- All cells are 'asically t#e same in c#emical composition-

E- All energy Jo( meta'olism O 'ioc#emistry! o$ li$e occurs (it#in cells-

As (it# t#e rapid gro(t# o$ molecular 'iology in t#e mid%20t# century, cell'iology researc# eploded in t#e 1BH0s- =t 'ecame possi'le to maintain,gro(, and manipulate cells outside o$ li"ing organisms- *#e &rst continuouscell line to 'e so cultured (as in 1BH1 'y <eorge tto <ey and co(orers,deri"ed $rom cer"ical cancer cells taen $rom enrietta .acs, (#o died $rom#er cancer in 1BH1- *#e cell line, (#ic# (as e"entually re$erred to as e.acells, #a"e 'een t#e (aters#ed in studying cell 'iology in t#e (ay t#at t#estructure o$ D9A (as t#e signi&cant 'reat#roug# o$ molecular 'iology-

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=n an a"alanc#e o$ progress in t#e study o$ cells, t#e coming decadeincluded t#e c#aracteri)ation o$ t#e minimal media re:uirements $or cellsand de"elopment o$ sterile cell culture tec#ni:ues- =t (as also aided 'y t#eprior ad"ances in electron microscopy, and later ad"ances suc# asde"elopment o$ trans$ection met#ods, disco"ery o$ green Juorescent proteinin Melly&s#, and disco"ery o$ small inter$ering ?9A si?9A!, among ot#ers-

A Ti/eline

!,3, – ansen credited (it# 1st compound microscope!0,, – ooe descri'ed TcellsI in cor-!01* – .eeu(en#oe disco"ered proto)oa- e sa( 'acteria some B yearslater-!2)) – /ro(n desci'ed t#e cell nucleus in cells o$ t#e orc#id-

!2)2 – Sc#leiden and Sc#(ann proposed cell t#eory-!2*5 – Al'rec#t "on ?oellier reali)ed t#at sperm cells and egg cells are alsocells-!2,0 – 9- Prings#eim o'ser"ed #o( a sperm cell penetrated an egg cell-!2,2 – ?udol$ irc#o( p#ysician, pat#ologist and ant#ropologist! epounds#is $amous conclusion+ omnis cellula e cellula, t#at is cells de"elop only $romeisting cells Kcells come $rom preeisting cellsL!2,1 – Uollier descri'ed mitoc#ondria-!213 – Flemming descri'ed c#romosome 'e#a"ior during mitosis-!22) – <erm cells are #aploid, c#romosome t#eory o$ #eredity-

!232 – <olgi descri'ed t#e golgi apparatus-!3)2 – /e#rens used di;erential centri$ugation to separate nuclei $romcytoplasm-!3)3 – Siemens produced t#e &rst commercial transmission electronmicroscope-!3,& – <ey and co(orers esta'lis#ed a continuous #uman cell line-!3,, – agle systematically de&ned t#e nutritional needs o$ animal cells inculture-!3,1 – 8eselson, Sta#l and inograd de"eloped density gradient

centri$ugation in cesium c#loride solutions $or separating nucleic acids-!30, – am introduced a de&ned serum%$ree medium- Cam'ridge=nstruments produced t#e &rst commercial scanning electron microscope-!310 – Sato and colleagues pu'lis# papers s#o(ing t#at di;erent cell linesre:uire di;erent mitures o$ #ormones and gro(t# $actors in serum%$reemedia-!32! – *ransgenic mice and $ruit Jies are produced- 8ouse em'ryonic stem

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cell line esta'lis#ed-!33, – *sien identi&es mutant o$ <FP (it# en#anced spectral properties!332 – 8ice are cloned $rom somatic cells-!333 – amilton and /aulcom'e disco"er si?9A as part o$ post%transcriptional gene silencing P*<S! in plants

T<O GENERAL T=PES OF CELLS

 *#ere are t(o types o$ cells+ uaryote  and proaryote- Proaryoticcells are usually independent, (#ile euaryotic cells can eit#er eist as asingle celled organism or 'e $ound in multicellular organisms-

Ta+le ! Co/'a(ison of fea#%(es of '(o6a(.o#ic and e%6a(.o#ic cells

  P(o6a(.o#es E%6a(.o#es

T.'ical o(ganis/s 'acteria, arc#aea protists, $ungi, plants, animals

T.'ical si>e V 1–H WmKL V 10–100 WmKL  sperm cells, apart $rom t#e tail, aresmaller!

T.'e of n%cle%snucleoid regionG no realnucleus

real nucleus (it# dou'le mem'rane

DNA circular usually! linear molecules c#romosomes! (it# #istone proteins

RNA4?'(o#ein4

s.n#-esiscoupled in cytoplasm

?9A%synt#esis inside t#e nucleusprotein synt#esis in cytoplasm

Ri+oso/es H0SX30S E0SX40S

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C.#o'las/a#ic

s#(%c#%(e"ery $e( structures #ig#ly structured 'y endomem'ranes and a cytoseleton

Cell /o$e/en# Jagella made o$Jagellin Jagella and cilia  containing microtu'ulesG  lamellipodiaand &lopodia containing actin

Mi#oc-ond(ia noneone to se"eral t#ousand t#oug# some lacmitoc#ondria!

C-lo(o'las#s none in algae and plants

O(gani>a#ion usually single cells single cells, colonies, #ig#er multicellular organisms (it#speciali)ed cells

Cell di$ision/inary &ssion simpledi"ision!

8itosis  &ssion or 'udding!8eiosis

P(o6a(.o#ic cells

 *#e proaryote cell is simpler, and t#ere$ore smaller, t#an a euaryote

cell, lacing a nucleus and most o$ t#e ot#er organelles o$ euaryotes- *#ereare t(o inds o$ proaryotes+ 'acteria  and arc#aeaG t#ese s#are a similarstructure-

 *#e nuclear material o$ a proaryotic cell consists o$ a singlec#romosome t#at is in direct contact (it# t#e cytoplasm- ere, t#e unde&nednuclear region in t#e cytoplasm is called t#e nucleoid-

A proaryotic cell #as t#ree arc#itectural regions+

• n t#e outside, Jagella and pili proMect $rom t#e cells sur$ace- *#eseare structures not present in all proaryotes! made o$ proteins t#at$acilitate mo"ement and communication 'et(een cells-

• nclosing t#e cell is t#e cell en"elope – generally consisting o$ a cell(all co"ering a plasma mem'rane t#oug# some 'acteria also #a"e a$urt#er co"ering layer called a capsule- *#e en"elope gi"es rigidity to

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t#e cell and separates t#e interior o$ t#e cell $rom its en"ironment,ser"ing as a protecti"e &lter- *#oug# most proaryotes #a"e a cell (all,t#ere are eceptions suc# as Mycoplasma  'acteria! andhermoplasma  arc#aea!- *#e cell (all consists o$  peptidoglycan  in'acteria, and acts as an additional 'arrier against eterior $orces- =t

also pre"ents t#e cell $rom epanding and &nally 'ursting cytolysis!$rom osmotic pressure  against a #ypotonic  en"ironment- Someeuaryote cells plant cells and $ungal cells! also #a"e a cell (all-

• =nside t#e cell is t#e cytoplasmic region t#at contains t#e cell genomeD9A! and ri'osomes and "arious sorts o$ inclusions- A proaryoticc#romosome is usually a circular molecule an eception is t#at o$ t#e'acterium !orrelia burgdorferi, (#ic# causes .yme disease!-K@L *#oug#not $orming a nucleus, t#e D9A is condensed in a nucleoid- Proaryotescan carry etrac#romosomal D9A elements called plasmids, (#ic# areusually circular- Plasmids ena'le additional $unctions, suc# as anti'iotic

resistance-

Diagram o$ a typical proaryotic cell

uaryotic cells

Plants, animals, $ungi, slime moulds, proto)oa, and algae are alleuaryotic- *#ese cells are a'out 1H times (ider t#an a typical proaryoteand can 'e as muc# as 1000 times greater in "olume- *#e maMor di;erence'et(een proaryotes and euaryotes is t#at euaryotic cells containmem'rane%'ound compartments in (#ic# speci&c meta'olic acti"ities taeplace- 8ost important among t#ese is a cell nucleus, a mem'rane%delineatedcompartment t#at #ouses t#e euaryotic cells D9A- *#is nucleus gi"es t#eeuaryote its name, (#ic# means >true nucleus-> t#er di;erences include+

•  *#e plasma mem'rane resem'les t#at o$ proaryotes in $unction, (it#minor di;erences in t#e setup- Cell (alls may or may not 'e present-

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•  *#e euaryotic D9A is organi)ed in one or more linear molecules,called c#romosomes, (#ic# are associated (it# #istone  proteins- Allc#romosomal D9A is stored in t#e cell nucleus, separated $rom t#ecytoplasm 'y a mem'rane- Some euaryotic organelles  suc# asmitoc#ondria also contain some D9A-

• 8any euaryotic cells are ciliated (it# primary cilia- Primary cilia playimportant roles in c#emosensation, mec#anosensation, andt#ermosensation- Cilia may t#us 'e >"ie(ed as sensory cellularantennae  t#at coordinate a large num'er o$ cellular signalingpat#(ays, sometimes coupling t#e signaling to ciliary motility oralternati"ely to cell di"ision and di;erentiation->KBL

• uaryotes can mo"e using motile cilia  or agella- *#e Jagella aremore comple t#an t#ose o$ proaryotes-

Ta+le & Co/'a(ison of s#(%c#%(es +e#8een ani/al and 'lan# cells

T.'ical ani/al cell T.'ical 'lan# cell

O(ganell

es

• 9ucleus 

o 9ucleolus (it#in nucleus!

• ?oug# endoplasmic reticulum ?!

• Smoot# ?

• ?i'osomes

• Cytoseleton

• <olgi apparatus

• Cytoplasm

• 8itoc#ondria

• esicles

• .ysosomes

• Centrosome 

• 9ucleus 

o 9ucleolus (it#in nucleus!

• ?oug# ?

• Smoot# ?

• ?i'osomes

• Cytoseleton

• <olgi apparatus dictiosomes!

• Cytoplasm

• 8itoc#ondria

• Plastids and its deri"ati"es

• acuoles!

• Cell (all

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o Centrioles

BASIC CELL FUNCTIONS

Cells #a"e e"ol"ed to contain many intricate structures inside o$ itsmem'rane- 8any o$ t#ese structures ser"e speci&c purposes- *#isinterconnected net(or o$ structures inside o$ a cell can 'e compared to t#esystem o$ gears inside o$ a simple mac#ine- ust as t#e gears #a"e tocooperate among t#emsel"es to ensure t#e mac#ines proper $unction, t#einternal organelles o$ a cell #a"e to interact to ensure t#e cells ultimate

sur"i"al-

 *#ere are se"eral main $unctions t#at t#e cell #as to carry out+molecule transport, reproduction, and energy con"ersion-

A- Properties o$ .i$e

•  *#e 'asic unit $or all li"ing organisms is t#e cell- rganisms can consisto$ a single cell 'acteria $or eample!, or many cells- =n morecomplicated organisms, cells are organi)ed to $orm more complicated

structures suc# as organs, $or eample- =n eac# o$ t#ese cells, uni:ue$orms o$ deoyri'onucleic acid D9A! molecules are present- D9A can$orm into genes, (#ic# are used to mae t#e proteins and ot#ermolecules a cell needs to sur"i"e and reproduce-

•  *o sur"i"e, organisms need to get energy- nergy is captured in many(ays, p#otosynt#esis using sunlig#t $or energy! 'eing one o$ t#em-

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 *#e (#ole set o$ c#emical reactions t#at cells use to recei"e energy iscalled meta'olism-

• rganisms also need to reproduce t#e production o$ o;spring 'y oneor more parents!- *#ere are t(o 'asic types o$ reproduction – aseual,

in (#ic# t#e cell simply splits in #al$, is common in single%cellorganisms- 8ore complicated organisms reproduce 'y seualreproduction 'y com'ing se cells gametes! $rom 'ot# parents- *#isproduces an o;spring (it# a com'ination o$ c#aracteristics $rom 'ot#parents- *#ese o;spring #a"e a greater c#ance o$ sur"i"al in c#angingconditions t#an aseually reproduced organisms 'ecause seuallyreproduced o;spring can adapt (#ile aseual production are simplyclones-

•

8utation is also an important c#aracteristic o$ li"ing organisms-8utations are random c#anges in t#e structure or composition o$ D9A,(#ic# can 'e caused 'y mistaes in reproduction or eternal e"ents,suc# as 5 damage- 8utations can 'e 'ene&cial, #arm$ul, or neutral-/ene&cial mutations #elp an organism adapt- rganisms (it#'ene&cial mutations #a"e a greater c#ance o$ sur"i"al, so o"er timet#ey 'ecome pre"alent- *#is process is called e"olution- =$ enoug#c#anges occur an entire ne( species can 'e $ormed t#er organisms(#ic# cannot adapt decline and may e"en 'ecome etinct- *#isongoing etinction and e"olution #a"e lead to a great amount o$ 

di"ersity on eart#-

/- 8olecule *ransport

 *(o main categories o$ molecule transport eist in cells, active

transport  and passive transport  s#o(n 'elo(!- For small molecules suc# asoygen, et#anol, and car'on dioide, t#e molecules could easily cross t#emem'rane "ia passi"e transport, in t#e $orm o$ simple di;usion t#roug# aconcentration gradient- o(e"er, t#e means t#at cells use to trans$er smallmolecules are not suZcient $or transporting macromolecules, (#ic# include

proteins, polynucleotides, and polysacc#arides- *o transport t#esemacromolecules, cells rely on acti"e transport- *#ere are t(o 'asic means o$ acti"e transport % 'y eocytosis and 'y endocytosis- ocytosis in"ol"essending macromolecules out o$ t#e cell, (#ile t#e opposite applies toendocytosis

E;oc.#osis

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8acromolecules t#at are released dont simply dri$t to(ards t#e cellsmem'rane and s:uee)e t#eir (ay out- *#ey are actually pacaged in a"esicle t#at separates t#em out $rom t#e rest o$ t#e cell- #e "esicle $uses(it# its speci&c mem'rane structure and its contents are released (it#outt#e "esicle, (#ic# is incorporated 'ac into t#e cells mem'rane-

Proteins, $or eample, t#at are to 'e secreted $rom t#e cell are madeon t#e roug# endoplasmic reticulum ?!- *#ey are t#en transported to t#e<olgi comple 'y ? induced "esicles- *#e <olgi comple sorts and pacagest#e proteins into "esicles t#at separate t#emsel"es o; t#e <olgi comple ande"entually $use (it# t#e cellular mem'rane-

Some molecules are secreted continually $rom t#e cell, 'ut ot#ers areselecti"ely secreted- *o control secretion, speci&c su'stances are stored in

secretory "esicles, (#ic# are released (#en triggered 'y an etracellularsignal- *#e signal, #ormones 'eing an eample, 'inds to its speci&c cellsur$ace receptor- *#en t#e concentration o$ $ree Ca2X is increased in t#e cell- *#e increased concentration o$ t#e Ca2X  triggers eocytosis, causing t#esecretory "esicles to $use (it# t#e cellular mem'rane, releasing t#esu'stances outside t#e cell-

Endoc.#osis

 *#ere are t(o types o$ endocytosis- #inocytosis  in"ol"es ingesting

small molecules and7or Juids surrounding t#e cell in a process no(n asJuid%p#ase endocytosis- #hagocytosis  in"ol"es t#e ingestion o$ largemolecules, suc# as microorganisms or cell de'ris using large "esicles, or"acuoles-

uaryotic cells are nearly continuously ingesting t#e surroundingJuids and molecules- =n doing so t#ey are also ingesting t#eir o(n cellularmem'rane at a rapid rate- 8acrop#ages, $or eample ingest 3N o$ its cellularmem'rane eac# minute, or 100N eac# #al$ and #our '"iously t#emem'rane is 'eing added 'y eocytosis at a'out t#e same rate it is 'eing

remo"ed 'y endocytosis-

8ost o$ t#e ingested molecules, (#ic# are surrounded 'y small "esiclescalled t#e primary "esicle, are $used (it# secondary lysosomes- *#emolecules t#at #a"e 'een ingested are t#en deposited at t#e cytosol, (#eret#e cell uses t#em and most o$ t#e "esicle is reintegrated into t#e cellular

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mem'rane- =n some cases t#e "esicle 'ypasses t#e secondary lysosome andgoes directly to its target-

$ten, a cell needs to selecti"ely ingest a molecule- For t#is case ituses a special process, called receptor$mediated endocytosis- *#e molecules

ingested 'ind to speci&c cell sur$ace receptors and are internali)ed at agreater rate t#an Juid is 'y Juid%p#ase endocytosis- An eample receptor%mediated endocytosis is t#e intae o$ lo(%density lipoproteins, or .D.- 6#ena cell needs c#olesterol to mae more mem'ranes it maes receptors $or .D.and places t#em in t#e cellular mem'rane- *#e .D. t#en 'inds to t#ereceptors and is rapidly taen in 'y t#e cell-

Some people contain de$ecti"e genes $or maing t#e cell sur$acereceptor $or .D.- *#ese people are una'le to ingest .D. and t#us #a"e a

#ig#er concentration o$ .D. in t#eir 'loodstream, gi"ing t#em a #ig#c#olesterol rate- *#ese people are more liely to die $rom #eart disease at anearly age-

P-agoc.#osis

6#ite 'lood cells use p#agocytosis to remo"e $oreign particles $romt#e 'lood stream- *#ese cells (ill literally engul$ $oreign particles t#at are t#esame si)e as itsel$- *#ere are t(o types o$ (#ite 'lood cells (#ic# act asp#agocytes+ macrop#ages and polymorp#ic leucocytes- *o 'e p#agocytosed,particles need to 'ind to t#e receptors on t#e p#agocyte- *#en t#e particle is

engul$ed and a'sor'ed-

CELL STRUCTURE LOCATION DESCRIPTION FUNCTION

Cell <all Plant, Fungi, O/acteria, 'ut not

animal cells• uter layer

• ?igid O strong

• 8ade o$cellulose

 

• Support gro(tall!

• Protection

• allo(s 2, 2,C2 to di;use inO out o$ cell

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Cell Me/+(ane

All cells

• Plant % insidecell (all

• Animal % outerlayerGc#olesterol

• Dou'le layer o$ p#osp#olipids(it# proteins

• Selecti"elypermea'le

• Support

• Protection

• Controlsmo"ement o$materials in7outo$ cell

• /arrier 'et(eencell and itsen"ironment

• 8aintains#omeostasis

N%cle%s

All cells eceptproaryotes

• .arge, o"al

• 8ay contain 1or morenucleoli

• olds D9A

• Controls cellacti"ities

• Contains t#e#ereditarymaterial o$ t#ecell

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N%clea( /e/+(ane

All cells eceptproaryotes

• Surroundsnucleus

• Dou'lemem'rane

• Selecti"elypermea'le

• Controls

mo"ement o$materials in7outo$ nucleus

C.#o'las/

All cells

• Clear, t#ic, Mellyliematerialcytosol!

• rganelles$ound insidecell mem'rane

• Contains t#ecytoseleton&'ers

• Supports andprotects cellorganelles

Endo'las/ic

(e#ic%l%/ @ER

All cells eceptproaryotes

• 9et(or o$tu'es or

mem'ranes

• Smoot# (7ori'osomes

• ?oug# (it#em'eddedri'osomes

• Connects tonuclearen"elope O cellmem'rane

• Carriesmaterialst#roug# cell

• Aids in maingproteins

Ri+oso/e All cells

• Small 'odies$ree orattac#ed to ?

• 8ade o$ r?9A

• Synt#esi)esproteins

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O protein

Mi#oc-ond(ion

All cells eceptproaryotes

• Peanut s#aped

• Dou'lemem'rane

• utermem'ranesmoot#

•

=nnermem'rane$olded intocristae

• /reas do(nsugar glucose!molecules torelease energy

• Site o$ aero'iccellularrespiration

ac%ole

  Plant cells #a"ea single, large

"acuole

Animal cells #a"e

small "acuoles

• Fluid%&lled sacs

• .argestorganelle in

plant cells

• Store $ood,(ater,meta'olic Otoic (astes

• Store large

amounts o$ $oodor sugars inplants

L.soso/e

Plant % uncommonAnimal % common

• Small andround (it# asinglemem'rane

• /reas do(nlarger $oodmolecules intosmallermolecules

• Digests old cellparts

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C-lo(o'las# 

Plants and algae

• <reen, o"alcontainingc#lorop#yllgreenpigment!

• Dou'lemem'rane(it# innermem'ranemodi&ed intosacs calledt#ylaoids

• Stacs o$t#ylaoidscalled grana Ointerconnected

• <el lieinnermostsu'stancecalled stroma

• 5ses energy$rom sun tomae $oodglucose! $or t#eplant

• Process calledp#otosynt#esis

• ?elease oygen

n%cleol%s

All cells eceptproaryotes

• Found insidet#e cellsnucleus

• 8ay #a"e moret#an one

• Disappearduring celldi"ision

• 8ae ri'osomes

Golgi A''a(a#%s

All cells eceptproaryotes   • Stacs o$

Jattened sacs

• a"e a cis Otrans $ace

• 8odi$y proteinsmade 'y t#e

cells

• Pacage Oeport proteins

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Cilia

Animal cells,Proto)oans

• a"e a B%2arrangemento$microtu'ules

• S#ort, 'utnumerous

 

• 8o"ement

 

Flagell%/

/acterial cells OProto)oans

• a"e a B%2arrangemento$microtu'ules

•

.ong, 'ut $e(in num'er

• 8o"ement

Cen#(ioles

Animal cells

• Pairedstructuresnear t#enucleus

• 8ade o$ acylinder o$microtu'ule

pairs

• Separatec#romosomepairs duringmitosis

C.#os6ele#on

All cells

• 8ade o$microtu'ulesmicro&laments

• Strengt#encell Omaintains t#es#ape

• 8o"esorganelles

(it#in t#e cell

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Cell Di$ision9 Mi#osis9 and Meiosis

Cell Di$ision F%nc#ions in Re'(od%c#ion9 G(o8#-9 and Re'ai( 

Cell di"ision in"ol"es t#e distri'ution o$ identical genetic material, D9A,to t(o daug#ters cells- 6#at is most remara'le is t#e &delity (it# (#ic# t#eD9A is passed along, (it#out dilution or error, $rom one generation to t#enet-

Co(e Conce'#s

• All rganisms Consist o$ Cells and Arise $rom Preeisting Cells

o 8itosis is t#e process 'y (#ic# ne( cells are generated-

o 8eiosis is t#e process 'y (#ic# gametes are generated $orreproduction-

•  *#e Cell Cycle ?epresents All P#ases in t#e .i$e o$ a Cell

o D9A replication S p#ase! must precede mitosis, so t#at alldaug#ter cells recei"e t#e same complement o$ c#romosomes ast#e parent cell-

o  *#e gap p#ases separate mitosis $rom S p#ase- *#is is t#e time(#en molecular signals mediate t#e s(itc# in cellular acti"ity-

o 8itosis in"ol"es t#e separation o$ copied c#romosomes intoseparate cells

• 5nregulated Cell Di"ision Can .ead to Cancer

o Cell%cycle c#ecpoints normally ensure t#at D9A replication andmitosis occur only (#en conditions are $a"ora'le and t#e processis (oring correctly-

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o 8utations in genes t#at encode cell%cycle proteins can lead tounregulated gro(t#, resulting in tumor $ormation and ultimatelyin"asion o$ cancerous cells to ot#er organs-

=n order to 'etter understand t#e concept o$ cell di"ision and genetics,

some 'asic de&nitions are in order+

• gene % 'asic unit o$ #eredityG codes $or a speci&c trait

• loc%s % t#e speci&c location o$ a gene on a c#romosome locus % pluralloci!

• geno/e % t#e total #ereditary endo(ment o$ D9A o$ a cell or organism

• so/a#ic cell % all 'ody cells ecept reproducti"e cells

• ga/e#e % reproducti"e cells i-e- sperm O eggs!

• c-(o/oso/e % elongate cellular structure composed o$ D9A andprotein % t#ey are t#e "e#icles (#ic# carry D9A in cells

• di'loid @&n % cellular condition (#ere eac# c#romosome type isrepresented 'y t(o #omologous c#romosomes

• -a'loid @n % cellular condition (#ere eac# c#romosome type isrepresented 'y only one c#romosome

• -o/ologo%s c-(o/oso/e % c#romosome o$ t#e same si)e and s#ape(#ic# carry t#e same type o$ genes

• c-(o/a#id % one o$ t(o duplicated c#romosomes connected at t#ecentromere

• cen#(o/e(e % region o$ c#romosome (#ere microtu'ules attac#during mitosis and meiosis

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C-(o/oso/e s#(%c#%(e

• composedo$ D9A andprotein

#istones!all tig#tly(rapped upin onepacage

• duplicatedc#romosomes areconnected'y a

centromere

%xample % an organism is 2n [ 4-

• C#romosomes 1 O 2 are #omologousc#romosomes

• C#romosomes 3 O 4 are #omologous

c#romosomes• C#romosomes 1 O 3 came $rom t#e mot#er

• C#romosomes 2 O 4 came $rom t#e $at#er

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T.'ical Ani/al Life C.cle

T-e Cell C.cle

G! % &rstgap

S % D9Asynt#esisreplication!

G& % secondgap

M % mitosis

• /i#osis  % nuclear7c#emical e"ents resulting in t(o daug#ter nuclei(#ic# #a"e identical genetic material to eac# ot#er and to t#e mot#ercell

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• c.#o6inesis  % di"ision o$ t#e cytoplasm- *#is usually occurs (it#mitosis, 'ut in some organisms t#is is not so

Mi#osis in a N%#s-ell

•  *#e stages o$ t#e cell cycle can 'e 'roen do(n into si stages+

o =nterp#ase, Prop#ase, 8etap#ase, Anap#ase, *elop#ase

In#e('-ase

• is t#e >resting> or non%mitotic portion o$ t#e cell cycle-

• =t is comprised o$ <1, S, and <2 stages o$ t#e cell cycle-

• D9A is replicated during t#e S p#ase o$ =nterp#ase

P(o'-ase % t#e &rst stage o$mitosis-

•  *#e c#romosomes condenseand 'ecome "isi'le

•  *#e centrioles $orm andmo"e to(ard opposite ends

o$ t#e cell >t#e poles>!

•  *#e nuclear mem'ranedissol"es

•  *#e mitotic spindle $orms$rom t#e centrioles inanimal cells!

• Spindle &'ers $rom eac#centriole attac# to eac#sister c#romatid at t#e

inetoc#ore

Compare Prop#ase to t#e Prop#ase=  and to t#e Prop#ase ==  stages o$ mitosis-

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Me#a'-ase 

•  *#e Centriolescomplete t#eirmigration to t#epoles

•  *#e c#romosomesline up in t#e middleo$ t#e cell >t#ee:uator>!

Compare 8etap#ase to t#e8etap#ase =  and to t#e8etap#ase ==  stages o$ 

mitosis- 

Ana'-ase 

• Spindles attac#ed to inetoc#ores'egin to s#orten-

•  *#is eerts a $orce on t#e sisterc#romatids t#at pulls t#em apart-

• Spindle &'ers continue tos#orten, pulling c#romatids toopposite poles-

•  *#is ensures t#at eac# daug#tercell gets identical sets o$ c#romosomes

Compare Anap#ase to t#e Anap#ase =and to t#e Anap#ase == stages o$ mitosis-

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Telo'-ase 

•  *#e c#romosomesdecondense

•  *#e nuclear en"elope$orms

• Cytoinesis reac#escompletion, creating t(odaug#ter cells

Compare *elop#ase to t#e *elop#ase = and to t#e *elop#ase== stages o$ mitosis-

C.#o6inesis Di$ides #-e C.#o'las/

=n animal cells, cytoinesis occurs 'y a process no(n as clea$age 

• First, a clea$age f%((o8 appears

o clea"age $urro( [ s#allo( groo"e near t#e location o$ t#e oldmetap#ase plate

• A contractile ring o$ actin micro&laments in association (it# myosin, aprotein

o Actin and myosin are also in"ol"ed in muscle contraction andot#er mo"ement $unctions

•  *#e contraction o$ a t#e di"iding cells ring o$ micro&laments is lie t#epulling o$ dra(strings

o  *#e cell is pinc#ed in t(o

• Cytoinesis in plant cells is di;erent 'ecause plant cells #a"e cell (alls-

•  *#ere is no clea"age $urro(

• During telop#ase, "esicles $rom t#e <olgi apparatus mo"e alongmicrotu'ules to t#e middle o$ t#e cell (#ere t#e cell plate (as! andcoalesce, producing t#e cell 'la#e 

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o Cell%(all construction materials are carried in t#e "esicles andare continually deposited until a complete cell (all $orms'et(een t#e t(o daug#ter cells

C-(o/oso/e Se'a(a#ion Is #-e e. E$en# of Mi#osis

• 8itotic spindle &'ers are t#e railroad tracs $or c#romosomemo"ement-

o Spindle &'ers are made o$ microtu'ules-

o 8icrotu'ules are lengt#ened and s#ortened 'y t#e addition andloss o$ tu'ulin su'units-

o 8itotic spindle s#ortening during anap#ase is a result o$ t#e losso$ tu'ulin su'units-

• A inetoc#ore motor is t#e engine t#at dri"es c#romosome mo"ement-

o 8ultiple studies #a"e s#o(n t#at t#e inetoc#ore contains motorproteins t#at can (al along t#e spindle &'er during anap#ase-

o  *#ese proteins presuma'ly remo"e tu'ulin su'units, s#orteningspindle &'ers and $acilitating t#e c#romosome mo"ement-

Reg%la#ion of #-e Cell C.cle

 *#e cell cycle is controlled 'y a cyclically operating set o$ reactionse:uences t#at 'ot# trigger and coordinate ey e"ents in t#e cell cycle

•  *#e cell%cycle control system is dri"en 'y a 'uilt%in cloc t#at can 'eadMusted 'y eternal stimuli c#emical messages!

• C-ec6'oin# % a critical control point in t#e cell cycle (#ere stop andgo%a#ead signals can regulate t#e cell cycle

o Animal cells #a"e 'uilt%in stop signals t#at #alt t#e cell cyclesand c#ecpoints until o"erridden 'y go%a#ead signals-

o  *#ree 8aMor c#ecpoints are $ound in t#e <1, <2, and 8 p#aseso$ t#e cell cycle

•  *#e <1 c#ecpoint % t#e ?estriction Point

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o  *#e <1 c#ecpoint ensures t#at t#e cell is large enoug# todi"ide, and t#at enoug# nutrients are a"aila'le to support t#eresulting daug#ter cells-

o =$ a cell recei"es a go%a#ead signal at t#e <1 c#ecpoint, it (ill

usually continue (it# t#e cell cycle

o =$ t#e cell does not recei"e t#e go%a#ead signal, it (ill eit t#ecell cycle and s(itc# to a non%di"iding state called <0

o Actually, most cells in t#e #uman 'ody are in t#e <0 p#ase

•  *#e <2 c#ecpoint ensures t#at D9A replication in S p#ase #as 'eencompleted success$ully-

•  *#e metap#ase c#ecpoint ensures t#at all o$ t#e c#romosomes are

attac#ed to t#e mitotic spindle 'y a inetoc#ore-

C.clins and C.clin4De'enden# inases 4 T-e Cell4C.cle Cloc6  ?#yt#mic Juctuations in t#e a'undance and acti"ity o$ cell%cycle control

molecules pace t#e e"ents o$ t#e cell cycle-

• inase % a protein (#ic# acti"ates or deacti"ates anot#er protein 'yp#osp#orylating t#em-

• Uinases gi"e t#e go%a#ead signals at t#e <1 and <2 c#ecpoints

•  *#e inases t#at dri"e t#ese c#ecpoints must t#emsel"es 'eacti"ated

o  *#e acti"ating molecule is a c.clin9  a protein t#at deri"es itsname $rom its cyclically Juctuating concentration in t#e cell

o /ecause o$ t#is re:uirement, t#ese inases are called c.clin4de'enden# 6inases, or Cd6s

MPF 4 Ma#%(a#ion P(o/o#ing Fac#o( @M4'-ase '(o/o#ing fac#o( 

• Cyclins accumulate during t#e <1, S, and <2 p#ases o$ t#e cell cycle

• /y t#e <2 c#ecpoint  t#e red 'ar in t#e &gure!, enoug# cyclin isa"aila'le to $orm 8PF complees aggregations o$ Cd and cyclin!(#ic# initiate mitosis

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o 8PF apparently $unctions 'y p#osp#orylating ey proteins in t#emitotic se:uence

• .ater in mitosis, 8PF s(itc#es itsel$ o; 'y initiating a process (#ic#leads to t#e destruction o$ cyclin

o Cd, t#e non%cyclin part o$ 8PF, persists in t#e cell as an inacti"e$orm until it associates (it# ne( cyclin molecules synt#esi)edduring interp#ase o$ t#e net round o$ t#e cell cycle

PDGF 4 Pla#ele#4De(i$ed G(o8#- Fac#o(s 4 An E;a/'le of an E;#e(nal

Signal fo( Cell Di$ision PD<F is re:uired $or t#e di"ision o$ &'ro'lasts (#ic# are essential in (ound#ealing

•

6#en inMury occurs, platelets 'lood cells important in 'lood clotting!release PD<F

• Fi'ro'lasts are a connecti"e tissue cells (#ic# possess PD<F receptorson t#eir plasma mem'ranes

•  *#e 'inding o$ PD<F acti"ates a signal%transduction pat#(ay t#at leadsto a proli$eration o$ &'ro'lasts and a #ealing o$ t#e (ound

Densi#. De'enden# In-i+i#ion 

• Cells gro(n in culture (ill rapidly di"ide until a single layer o$ cells isspread o"er t#e area o$ t#e petri dis#, a$ter (#ic# t#ey (ill stopdi"iding

• =$ cells are remo"ed, t#ose 'ordering t#e open space (ill 'egin di"idingagain and continue to do so until t#e gap is &lled % t#is is no(n ascon#ac# in-i+i#ion 

• Apparently, (#en a cell population reac#es a certain density, t#eamount o$ re:uired gro(t# $actors and nutrients a"aila'le to eac# cell

'ecomes insuZcient to allo( continued cell gro(t#Anc-o(age De'endence 

• For most animal cells to di"ide, t#ey must 'e attac#ed to a su'stratum,suc# as t#e etracellular matri o$ a tissue or t#e inside o$ t#e culture Mar

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• Anc#orage is signaled to t#e cell%cycle control system "ia pat#(aysin"ol"ing mem'rane proteins and t#e cytoseleton

Cells <-ic- No Longe( Res'ond #o Cell4C.cle Con#(ols 4 Cance( Cells 

• Cancer cells do not respond normally to t#e 'odys control mec#anism-

o  *#ey di"ide ecessi"ely and in"ade ot#er tissues

o =$ le$t unc#eced, t#ey can ill t#e organism

• Cancer cells do not e#i'it contact in#i'ition

o =$ cultured, t#ey continue to gro( on top o$ eac# ot#er (#en t#etotal area o$ t#e petri dis# #as 'een co"ered

o  *#ey may produce re:uired eternal gro(t# $actor or o"erride$actors! t#emsel"es or possess a'normal signal transductionse:uences (#ic# $alsely con"ey gro(t# signals t#ere'y'ypassing normal gro(t# c#ecs

• Cancer cells e#i'it irregular gro(t# se:uences

o =$ gro(t# o$ cancer cells does cease, it does so at random pointso$ t#e cell cycle

o Cancer cells can go on di"iding inde&nitely i$ t#ey are gi"en acontinual supply o$ nutrients

9ormal mammalian cells gro(ing in culture only di"ide 20%H0 times 'e$ore t#ey stop di"iding

Meiosis

Mo(e deni#ions

•Allele % alternate $orms o$ t#e same gene

• Ho/o>.go%s % #a"ing t(o identical alleles $or a gi"en gene

• He#e(o>.go%s % #a"ing t(o di;erent alleles $or a gi"en gene

• Geno#.'e % genetic maeup o$ an organism

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• P-eno#.'e % t#e epressed traits o$ an organism

Meiosis in a N%#s-ell

• 8eiosis =s a Special *ype o$ Cell Di"ision *#at ccurs in Seually

?eproducing rganisms

o 8eiosis reduces t#e c#romosome num'er 'y #al$, ena'lingseual recom'ination to occur-

8eiosis o$ diploid cells produces #aploid daug#ter cells,(#ic# may $unction as gametes-

<ametes undergo $ertili)ation, restoring t#e diploid num'ero$ c#romosomes in t#e )ygote

o 8eiosis and $ertili)ation introduce genetic "ariation in t#ree(ays+

Crossing o"er 'et(een #omologous c#romosomes atprop#ase =-

=ndependent assortment o$ #omologous pairs atmetap#ase =+

ac# #omologous pair can orient in eit#er o$ t(o

(ays at t#e plane o$ cell di"ision-

 *#e total num'er o$ possi'le outcomes [ 2n n [num'er o$ #aploid c#romosomes!-

?andom c#ance $ertili)ation 'et(een any one $emalegamete (it# any ot#er male gamete-

•  *#e ?ole o$ Seual ?eproduction in "olution

o Seual reproduction in a population s#ould decline in $re:uency

relati"e to aseual reproduction-

Aseual reproduction 9o males are needed, all indi"idualscan produce o;spring-

Seual reproduction nly $emales can produce o;spring,t#ere$ore $e(er are produced-

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o Seual reproduction may eist 'ecause it pro"ides genetic"aria'ility t#at reduces suscepti'ility o$ a population to pat#ogenattac-

 *#e stages o$ meiosis can 'e 'roen do(n into t(o main stages, Meiosis

I and Meiosis II 

• Meiosis I  can 'e 'roen do(n into $our su'stages+ Prop#ase =,8etap#ase =, Anap#ase = and *elop#ase =

• Meiosis II  can 'e 'roen do(n into $our su'stages+ Prop#ase ==,8etap#ase ==, Anap#ase == and *elop#ase ==

Meiosis I

P(o'-ase I  % most o$ t#e signi&cant processes o$ 8eiosis occur during Prop#ase =

•  *#e c#romosomes condense and 'ecome "isi'le

•  *#e centrioles $orm and mo"e to(ard t#e poles

•  *#e nuclear mem'rane 'egins to dissol"e

•  *#e #omologs pair up, $orming a tetrad

o ac# tetrad is comprised o$ $ourc#romotids % t#e t(o #omologs, eac# (it#t#eir sister c#romatid

• omologous c#romosomes (ill s(ap geneticmaterial in a process no(n as c(ossing o$e(a''re"iated as \!

o Crossing o"er ser"es to inc(ease gene#ic

di$e(si#.  'y creating $our uni:uec#romatids

Compare Prop#ase = to Prop#ase == and to t#e Prop#asestage o$ mitosis-

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Me#a'-ase I 

• 8icrotu'ules gro( $rom t#e centrioles and attac#

to t#e centromeres

•  *#e tetrads line up along t#e cell e:uator

Compare 8etap#ase = to 8etap#ase ==  and to t#e8etap#ase stage o$ mitosis-

Ana'-ase I 

•  *#e centromeres 'rea and -o/ologo%s

c-(o/oso/es  separate note t#at t#e sis#e(c-(o/a#ids are still attac#ed!

• Cytoinesis 'egins

Compare Anap#ase = to Anap#ase ==  and to t#eAnap#ase stage o$ mitosis-

Telo'-ase I 

•  *#e c#romosomes may decondense depends onspecies!

• Cytoinesis reac#es completion, creating #8o

-a'loid da%g-#e( cells

Compare *elop#ase = to  *elop#ase ==  and to t#e *elop#ase stage o$ mitosis-

 

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Meiosis II

P(o'-ase II 

• Centrioles $orm and mo"e to(ard t#e poles

•  *#e nuclear mem'rane dissol"es

Compare Prop#ase == to Prop#ase = and to t#e Prop#ase stage o$ mitosis-

Me#a'-ase II 

• 8icrotu'ules gro( $rom t#e centrioles and attac# to t#ecentromeres

•  *#e sister c#romatids line up along t#e cell e:uator

Compare 8etap#ase == to 8etap#ase = and to t#e 8etap#ase stage o$ 

mitosis-

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Ana'-ase II 

•  *#e centromeres 'rea and sis#e( c-(o/a#ids separate

• Cytoinesis 'egins

Compare Anap#ase == to Anap#ase = and to t#e  Anap#ase stage o$ mitosis-

Telo'-ase II 

•  *#e c#romosomes may decondense depends onspecies!

• Cytoinesis reac#es completion, creating fo%(

-a'loid da%g-#e( cells

Compare *elop#ase == to  *elop#ase =  and to t#e *elop#ase stage o$ mitosis-

 

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A Co/'a(ison +e#8een Mi#osis and Meiosis

T-e Conse%ences of Meio#ic Mis#a6es

9ondisMunctions occur (#en #omologous c#romosomes $ail to separate atmeiosis = or (#en c#romatids $ail to separate at meiosis ==-

• Fertili)ation can result in em'ryos t#at are 2n X 1 a >trisomy>! or 2n ]1-

• A'normal copy num'ers o$ one or more c#romosomes is usually, 'utnot al(ays, $atal ample+ Do(n syndrome!

Polyploidy can occur (#en (#ole sets o$ c#romosomes $ail to separate at

meiosis = or ==-

•  *#e resulting 2n gametes, i$ $ertili)ed 'y normal sperm, create 3n)ygotes triploid!-

• rganisms (it# an odd num'er o$ c#romosome sets cannot produce"ia'le gametes ample+ seedless $ruits!-

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THE CELL C=CLE

 *#e cell c.cle, or cell4di$ision c.cle, is t#e series o$ e"ents t#at taeplace in a cell leading to its di"ision and duplication replication!- =n cells(it#out a nucleus proaryotic!, t#e cell cycle occurs "ia a process termed'inary &ssion- =n cells (it# a nucleus euaryotes!, t#e cell cycle can 'edi"ided in t(o periods+ interp#ase^during (#ic# t#e cell gro(s,accumulating nutrients needed $or mitosis and duplicating its D9A^and t#emitotic 8! p#ase, during (#ic# t#e cell splits itsel$ into t(o distinct cells,o$ten called >daug#ter cells> and t#e &nal p#ase, cytoinesis, (#ere t#e ne(cell is completely di"ided- *#e cell%di"ision cycle is a "ital process 'y (#ic# a

single%celled $ertili)ed egg de"elops into a mature organism, as (ell as t#eprocess 'y (#ic# #air, sin, 'lood cells, and some internal organs  arerene(ed-

P-ases

 *#e cell cycle consists o$ $our distinct p#ases+ <1  p#ase, S p#asesynt#esis!, <2  p#ase  collecti"ely no(n as interp#ase! and 8 p#asemitosis!- 8 p#ase is itsel$ composed o$ t(o tig#tly coupled processes+mitosis, in (#ic# t#e cells c#romosomes are di"ided 'et(een t#e t(o sister

cells, and cytoinesis, in (#ic# t#e cells cytoplasm di"ides in #al$ $ormingdistinct cells- Acti"ation o$ eac# p#ase is dependent on t#e properprogression and completion o$ t#e pre"ious one- Cells t#at #a"e temporarilyor re"ersi'ly stopped di"iding are said to #a"e entered a state o$ :uiescencecalled <0 p#ase-

S#a#eDesc(i'#io

nA++(e$ia#ion

:uiescent7

senescent

<ap 0 G5

A resting p#ase (#ere t#e cell #as le$t t#e cycle and

#as stopped di"iding-

=nterp#ase

<ap 1 G! Cells increase in si)e in <ap 1- *#e &'  chec(point 

control mec#anism ensures t#at e"eryt#ing is ready $orD9A synt#esis-

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Synt#esis S D9A replication occurs during t#is p#ase-

<ap 2 G&

During t#e gap 'et(een D9A synt#esis and mitosis, t#ecell (ill continue to gro(- *#e &)  chec(point   controlmec#anism ensures t#at e"eryt#ing is ready to entert#e 8 mitosis! p#ase and di"ide-

Celldi"ision

8itosis M

Cell gro(t# stops at t#is stage and cellular energy is$ocused on t#e orderly di"ision into t(o daug#ter cells-A c#ecpoint in t#e middle o$ mitosis Metaphase

*hec(point ! ensures t#at t#e cell is ready to completecell di"ision-

A$ter cell di"ision, eac# o$ t#e daug#ter cells 'egin t#e interp#ase o$ a

ne( cycle- Alt#oug# t#e "arious stages o$ interp#ase are not usuallymorp#ologically distinguis#a'le, eac# p#ase o$ t#e cell cycle #as a distinctset o$ speciali)ed 'ioc#emical processes t#at prepare t#e cell $or initiation o$ cell di"ision-

<0 p#ase

 *#e term >post%mitotic> is sometimes used to re$er to 'ot# :uiescentand senescent  cells- 9onproli$erati"e cells in multicellular euaryotesgenerally enter t#e :uiescent <0 state $rom <1 and may remain :uiescent $or

long periods o$ time, possi'ly inde&nitely as is o$ten t#e case $or neurons!- *#is is "ery common $or cells t#at are $ully di;erentiated- Cellularsenescence occurs in response to D9A damage or degradation t#at (ouldmae a cells progeny non"ia'leG it is o$ten a 'ioc#emical reactionG di"ision o$ suc# a cell could, $or eample, 'ecome cancerous- Some cells enter t#e < 0

p#ase semi%permanentally e-g-, some li"er and idney cells-

Interphase

/e$ore a cell can enter cell di"ision, it needs to tae in nutrients- All o$ t#e preparations are done during t#e interp#ase- =nterp#ase proceeds int#ree stages, <1, S, and <2- Cell di"ision operates in a cycle- *#ere$ore,interp#ase is preceded 'y t#e pre"ious cycle o$ mitosis and cytoinesis-=nterp#ase is also no(n as preparatory p#ase- =n t#is stage nucleus andcytosol di"ision does not occur- *#e cell prepares $or di"ision- *#e inacti"e c#romose can 'e seen attac#ed to nuclear mem'rane in t#is p#ase

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G1 phase

 *#e &rst p#ase (it#in interp#ase, $rom t#e end o$ t#e pre"ious 8 p#aseuntil t#e 'eginning o$ D9A synt#esis is called <1 < indicating gap!- =t is alsocalled t#e gro(t# p#ase- During t#is p#ase t#e 'iosynt#etic acti"ities o$ t#ecell, (#ic# #ad 'een considera'ly slo(ed do(n during 8 p#ase, resume at a#ig# rate- *#is p#ase is mared 'y t#e use o$ 20 amino acids to $orm millionso$ proteins and later on en)ymes t#at are re:uired in S p#ase, mainly t#oseneeded $or D9A replication- Duration o$ <1 is #ig#ly "aria'le, e"en amongdi;erent cells o$ t#e same species- =t is under t#e control o$ t#e pH3 gene-

S phase

 *#e ensuing S p#ase starts (#en D9A replication commencesG (#en itis complete, all o$ t#e c#romosomes  #a"e 'een replicated, i-e-, eac#c#romosome #as t(o sister! c#romatids- *#us, during t#is p#ase, t#e

amount o$ D9A in t#e cell #as e;ecti"ely dou'led, t#oug# t#e ploidy o$ t#ecell remains t#e same- During t#is p#ase, synt#esis is completed as :uiclyas possi'le due to t#e eposed 'ase pairs 'eing sensiti"e to eternal $actorssuc# as any drugs taen or any mutagens suc# as nicotine!-

G2 phase

During t#e gap 'et(een D9A synt#esis and mitosis, t#e cell (illcontinue to gro(- *#e <2 c#ecpoint control mec#anism ensures t#ate"eryt#ing is ready to enter t#e 8 mitosis! p#ase and di"ides

8itosis 8 p#ase, mitotic p#ase!

 *#e relati"ely 'rie$ M phase  consists o$ nuclear di"ision aryoinesis!- *#e 8 p#ase #as 'een 'roen do(n into se"eral distinct p#ases, se:uentiallyno(n as+

• prop#ase,

• metap#ase,

•

anap#ase,

• telop#ase

• cytoinesis strictly speaing, cytoinesis is not part o$ mitosis 'ut isan e"ent t#at directly $ollo(s mitosis in (#ic# cytoplasm is di"ided intot(o daug#ter cells!

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Mi#osis  is t#e process 'y (#ic# a euaryotic  cell separates t#ec#romosomes  in its cell nucleus  into t(o identical sets in t(o nuclei- =t isgenerally $ollo(ed immediately 'y cytoinesis, (#ic# di"ides t#e nuclei,cytoplasm, organelles and cell mem'rane into t(o cells containing roug#lye:ual s#ares o$ t#ese cellular components- 8itosis and cytoinesis toget#erde&ne t#e /i#o#ic @M '-ase o$ t#e cell cycle % t#e di"ision o$ t#e mot#ercell into t(o daug#ter cells, genetically identical to eac# ot#er and to t#eirparent cell- *#is accounts $or approimately 10N o$ t#e cell cycle-

8itosis occurs eclusi"ely in euaryotic cells, 'ut occurs in di;erent (aysin di;erent species- For eample, animals undergo an >open> mitosis, (#eret#e nuclear en"elope 'reas do(n 'e$ore t#e c#romosomes separate, (#ile$ungi  suc# as  +spergillus nidulans  and ,accharomyces cerevisiae  yeast!undergo a >closed> mitosis, (#ere c#romosomes di"ide (it#in an intact cell

nucleus- 

Proaryotic cells, (#ic# lac a nucleus, di"ide 'y a process called'inary &ssion-

 *#e process o$ mitosis is comple and #ig#ly regulated- *#e se:uence o$ e"ents is di"ided into p#ases, corresponding to t#e completion o$ one set o$ acti"ities and t#e start o$ t#e net- *#ese stages are prop#ase,prometap#ase, metap#ase, anap#ase and telop#ase- During t#e process o$ mitosis t#e pairs o$ c#romosomes condense and attac# to &'ers t#at pull t#esister c#romatids  to opposite sides o$ t#e cell- *#e cell t#en di"ides incytoinesis, to produce t(o identical daug#ter cells-

/ecause cytoinesis usually occurs in conMunction (it# mitosis, >mitosis>is o$ten used interc#angea'ly (it# >8 p#ase>- o(e"er, t#ere are many cells(#ere mitosis and cytoinesis occur separately, $orming single cells (it#multiple nuclei in a process called endoreplication- *#is occurs most nota'lyamong t#e $ungi and slime moulds, 'ut is $ound in "arious groups- "en inanimals, cytoinesis and mitosis may occur independently, $or instanceduring certain stages o$ $ruit Jy em'ryonic de"elopment-K rrors in mitosiscan eit#er ill a cell t#roug# apoptosis or cause mutations t#at may lead tocancer-