DNA Ekstrakromosomal,.pptx

8/18/2019 DNA Ekstrakromosomal,.pptx

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Soraya Rahmanisa

DNA Ekstrakromosomal,Sifat, dan Kegunaannya


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Pengertian

DNA ekstrakromosomal : DNAlain yang terdapat dalam sel diluar nukleus, yaitu :

- DNA mitokondria, DNAkloroplas, DNA plasmid


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The Genome Defnes the Program o Multicellular

Development The cells in an indi!idual animal or plant are e"traordinarily !aried# $at cells,skin cells, %one cells, ner!ecells&they seem as dissimilar as any cells 'ould%e# (et all these 'ell types are generated during em%ryoni' de!elopment froma single fertili)ed egg 'ell, and all *+ith minor e"'eptions 'ontain identi'al'opies of thegenome of the spe'ies#

The e"planation lies in the +ay in +hi'h these cells make sele'ti!e use of theirgeneti' instru'tions a''ording to the 'ues they get from their surroundings#

The DNA is not ust a shopping list spe'ifying the mole'ules that e!ery 'ellmust ha!e, and the 'ell is not an assem%ly of all the items on the list# Rather,the 'ell %eha!es as a multipurpose ma'hine, +ith sensors to re'ei!een!ironmental signals and highly de!eloped a%ilities to 'all di.erent sets ofgenes into a'tion a''ording to the se/uen'es of signals to +hi'h the 'ell has%een e"posed# A large fra'tion of the genes in the eu'aryoti' genome 'ode forproteins that ser!e to regulate the a'ti!ities of other genes# 0ost of these gene

regulatory proteins a't %y %inding, dire'tly or indire'tly, to the regulatory DNAada'ent to the genes that are to %e 'ontrolled *$igure 1-23, or %y interfering+ith the a%ilities of other proteins to do so# The e"panded genome ofeu'aryotes therefore ser!es not only to spe'ify the hard+are of the 'ell, %utalso to store the soft+are that 'ontrols ho+ that hard+are is used#

http://www.ncbi.nlm.nih.gov/books/NBK26909/figure/A84/?report=objectonlyhttp://www.ncbi.nlm.nih.gov/books/NBK26909/figure/A84/?report=objectonly


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Eucaryotic Genomes Are Rich in RegulatoryDNA

0u'h of our non'oding DNA is almost 'ertainlydispensa%le unk, retained like a mass of old papers%e'ause, +hen there is little pressure to keep anar'hi!e small, it is easier to retain e!erything thanto sort out the !alua%le information and dis'ard therest# 4ertain e"'eptional eu'aryoti' spe'ies, su'h

as the pu.er 5sh *$igure 1-67, %ear +itness to thepro8iga'y of their relati!es9 they ha!e someho+managed either to rid themsel!es of large

/uantities of non'oding DNA, or to ha!e a!oideda'/uiring it in the 5rst pla'e# (et they appearsimilar in stru'ture, %eha!ior, and 5tness to relatedspe'ies that ha!e !astly more su'h DNA#

http://www.ncbi.nlm.nih.gov/books/NBK26909/figure/A82/?report=objectonlyhttp://www.ncbi.nlm.nih.gov/books/NBK26909/figure/A82/?report=objectonly


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DNA- inheritan'e %lueprint

- 'onsist the genes *fun'tional units- 'o!ered into 'hromosome4hromosomal a%erration in'lude the genes *multi genes


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The pu.er 5sh (Fugu rubripes).# Thisorganism has a genome si)e of 233 millionnu'leotide pairs&a%out one-/uarter asmu'h as a )e%ra5sh, for e"ample, e!en

though the t+o spe'ies of 5sh ha!e similarnum%ers of genes# *$rom a +ood'ut %y;iroshige,


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E!en in 'ompa't eu'aryoti' genomes su'h asthat of pu.er 5sh, there is more non'oding

DNA than 'oding DNA, and at least some of

the non'oding DNA 'ertainly has important

fun'tions#


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The Mouse Serves as a Moel or Mammals

0ammals ha!e typi'ally three or four times as many genesas Drosophila, a genome that is >3 times larger, and millions or %illions oftimes as many cells in their adult %odies#


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;uman and mouse:similar genes andsimilar de!elopment#

The human %a%y andthe mouse sho+nhere ha!e similar+hite pat'hes on theirforeheads %e'ause

%oth ha!e mutationsin the same gene*'alled kit),re/uiredfor the de!elopmentand maintenan'e ofpigment

Sour'e : 0ole'ular?iology of the 4ell#2th edition#

Al%erts ?, ohnson A,e+is , et al#

Ne+ (ork:Farland S'ien'e9>33>#

http://www.garlandscience.com/textbooks/0815341059.asphttp://www.garlandscience.com/textbooks/0815341059.asp


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Eu'aryoti' cells, %y de5nition, keep their DNA in a separate mem%rane-%ounded'ompartment, the nu'leus# They ha!e, in addition, a 'ytoskeleton for mo!ement, ela%orateintra'ellular 'ompartments for digestion and se'retion, the 'apa'ity *in many spe'ies toengulf other cells, and a meta%olism that depends on the o"idation of organi' mole'ules %ymito'hondria# These properties suggest that eu'aryotes originated as predators on other cells#0ito'hondria&and, in plants, 'hloroplasts&'ontain their o+n geneti' material, and e!identlye!ol!ed from %a'teria that +ere taken up into the 'ytoplasm of the eu'aryoti' 'ell andsur!i!ed as sym%ionts# Eu'aryoti' cells ha!e typi'ally 6G63 times as many genes aspro'aryotes, and often thousands of times more non'oding DNA# The non'oding DNA allo+s for

'omple" regulation of gene e"pression, as re/uired for the 'onstru'tion of 'omple"multi'ellular organisms# 0any eu'aryotes are, ho+e!er, uni'ellular, among them the

yeast Saccharomyces cerevisiae, +hi'h ser!es as a simple model organism for eu'aryoti' 'ell%iology, re!ealing the mole'ular %asis of 'onser!ed fundamental pro'esses su'h as theeu'aryoti' 'ell di!ision 'y'le# A small num%er of other organisms ha!e %een 'hosen as primarymodels for multi'ellular plants and animals, and the se/uen'ing of their entire genomes hasopened the +ay to systemati' and 'omprehensi!e analysis of gene fun'tions, gene regulation,and geneti' di!ersity# As a result of gene dupli'ations during !erte%rate e!olution,!erte%rate

genomes 'ontain multiple 'losely related homologs of most genes# This geneti'

redundan'y has allo+ed di!ersi5'ation and spe'iali)ation of genes for ne+ purposes, %ut it

also makes gene fun'tions harder to de'ipher# There is less geneti' redundan'y in thenematode Caenorhabditis elegans and the 8y Drosophila melanogaster, +hi'h ha!e thusplayed a key part in re!ealing uni!ersal geneti' me'hanisms of animal de!elopment#

http://www.ncbi.nlm.nih.gov/books/n/mboc4/A4754/def-item/A5107/http://www.ncbi.nlm.nih.gov/books/n/mboc4/A4754/def-item/A5107/http://www.ncbi.nlm.nih.gov/books/n/mboc4/A4754/def-item/A5107/http://www.ncbi.nlm.nih.gov/books/n/mboc4/A4754/def-item/A5107/


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Eucaryotic DNA !s Pac"age into a Set o #hromosomes

2 di.erent'hromosomes# Ea'h'hromosome 'onsists of a single, enormously long linear DNA mole'ule asso'iated

+ith proteins that fold and pa'k the 5ne DNA thread into a more 'ompa't stru'ture# The'omple" ofDNA and protein is 'alled chromatin*from the Freek chroma, I'olor,J %e'ause of its staining

properties#


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Nucleosomes Are the &asic 'nit o Eucaryotic#hromosome Structure

The proteins that %ind to the DNA to form eu'aryoti' 'hromosomes aretraditionally di!ided into t+o general 'lasses: the histones andthe nonhistone chromosomal proteins# The 'omple" of %oth 'lasses ofprotein +ith the nu'lear DNA of eu'aryoti' cells is kno+n as 'hromatin#;istones are present in su'h enormous /uantities in the 'ell *a%out 3million mole'ules of ea'h type per human 'ell that their total mass in'hromatin is a%out e/ual to that of the DNA#

;istones are responsi%le for the 5rst and most %asi' le!el of 'hromosome organi)ation, the nu'leosome, +hi'h +as dis'o!ered in 17C2# =heninterphase nu'lei are %roken open !ery gently and their 'ontentse"amined under the ele'tron mi'ros'ope, most of the 'hromatin is in theform of a 5%er +ith a diameter of a%out 63 nm*$igure 2->6A#


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Stru'turalorgani)ation of

thenu'leosome# Anu'leosome'ontains aprotein 'oremade of eight

histonemole'ules# Asindi'ated, thenu'leosome'ore parti'le isreleased from'hromatin %ydigestion ofthe linker DNA+ith anu'lease, anen)yme that%reaks


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Ea'h nu'leosome 'ore parti'le is separated from thene"t %y a region of linker DNA, +hi'h 'an !ary inlength from a fe+ nu'leotide pairs up to a%out @3# *Theterm nucleosome te'hni'ally refers to a nu'leosome'ore parti'le plus one of its ada'ent DNA linkers, %ut it

is often used synonymously +ith nu'leosome 'oreparti'le# Mn a!erage, therefore, nu'leosomes repeatat inter!als of a%out >33 nu'leotide pairs# $or e"ample,a diploidhuman 'ell +ith #2 H 137 nu'leotide pairs'ontains appro"imately 63 million nu'leosomes# The

formation of nu'leosomes 'on!erts a DNA mole'ule into a 'hromatin thread a%out one-third of its initiallength, and this pro!ides the 5rst le!el of DNA pa'king#

http://www.ncbi.nlm.nih.gov/books/n/mboc4/A4754/def-item/A5566/http://www.ncbi.nlm.nih.gov/books/n/mboc4/A4754/def-item/A5084/http://www.ncbi.nlm.nih.gov/books/n/mboc4/A4754/def-item/A5567/http://www.ncbi.nlm.nih.gov/books/n/mboc4/A4754/def-item/A5077/http://www.ncbi.nlm.nih.gov/books/n/mboc4/A4754/def-item/A5486/http://www.ncbi.nlm.nih.gov/books/n/mboc4/A4754/def-item/A4974/http://www.ncbi.nlm.nih.gov/books/n/mboc4/A4754/def-item/A4974/http://www.ncbi.nlm.nih.gov/books/n/mboc4/A4754/def-item/A5486/http://www.ncbi.nlm.nih.gov/books/n/mboc4/A4754/def-item/A5077/http://www.ncbi.nlm.nih.gov/books/n/mboc4/A4754/def-item/A5567/http://www.ncbi.nlm.nih.gov/books/n/mboc4/A4754/def-item/A5084/http://www.ncbi.nlm.nih.gov/books/n/mboc4/A4754/def-item/A5566/


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The Stru'ture of DNA Pro!ides a 0e'hanism for;eredity


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Fenes 'arry %iologi'al information that must %e 'opied a''urately for transmission to the ne"t generationea'h time a 'ell di!ides to form t+o daughter 'ells# T+o 'entral %iologi'al /uestions arise from thesere/uirements: ho+ 'an the information for spe'ifying an organism %e 'arried in 'hemi'al form, and ho+ isit a''urately 'opied The dis'o!ery of the structure of the DNA dou%le heli" +as a landmark int+entieth-'entury %iology %e'ause it immediately suggested ans+ers to %oth /uestions, there%y resol!ingat the mole'ular le!el the pro%lem of heredity# =e dis'uss %rie8y the ans+ers to these /uestions in thisse'tion, and +e shall e"amine them in more detail in su%se/uent 'hapters#

DNA en'odes information through the order, or se/uen'e, of the nu'leotides along ea'h strand# Ea'h %ase&A, 4, T, or F&'an %e 'onsidered as a letter in a four-letter alpha%et that spells out %iologi'al messagesin the 'hemi'al structure of the DNA# As +e sa+ in 4hapter 1, organisms di.er from one another

%e'ause their respe'ti!e DNA mole'ules ha!e di.erent nu'leotide se/uen'es and, 'onse/uently, 'arrydi.erent %iologi'al messages# ?ut ho+ is the nu'leotide alpha%et used to make messages, and +hat dothey spell out

As dis'ussed a%o!e, it +as kno+n +ell %efore the structure of DNA +as determined that genes 'ontainthe instru'tions for produ'ing proteins# The DNA messages must therefore someho+ en'ode proteins *$igure 2-# This relationship immediately makes the pro%lem easier to understand, %e'ause of the'hemi'al 'hara'ter of proteins# As dis'ussed in 4hapter 6, the properties of a protein, +hi'h areresponsi%le for its %iologi'alunction, are determined %y its three-dimensional structure, andits structure is determined in turn %y the linear se/uen'e of the amino a'ids of +hi'h it is 'omposed# The

linear se/uen'e of nu'leotides in a gene must therefore someho+ spell out the linear se/uen'e of aminoa'ids in a protein# The e"a't 'orresponden'e %et+een the four-letter nu'leotide alpha%et of DNA and thet+enty-letter amino a'id alpha%et of proteins&thegeneti' 'ode&is not o%!ious from the DNA structure,and it took o!er a de'ade after the dis'o!ery of thedou%le heli" %efore it +as +orked out#


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The 'omplete set of information in an organismOs DNA is'alled its genome, and it 'arries the information for allthe proteins the organism +ill e!er synthesi)e# *The termgenome is also used to des'ri%e the DNA that 'arries thisinformation# The amount of information 'ontained in

genomes is staggering: for e"ample, a typi'al human 'ell'ontains > meters of DNA# =ritten out in the four-letternu'leotide alpha%et, the nu'leotide se/uen'e of a !erysmall human gene o''upies a /uarter of a page of te"t *$igure 2-C, +hile the 'omplete se/uen'e of nu'leotidesin the human genome +ould 5ll more than a thousand%ooks the si)e of this one#


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!n Eucaryotes( DNA !s Enclose in a #ellNucleus

Nearly all the DNA in a eu'aryoti' 'ell is se/uestered ina nu'leus, +hi'h o''upies a%out 13B of the total 'ell!olume# This 'ompartment is delimited %y anuclear envelope formed %y t+o 'on'entri' lipid %ilayer mem%ranes that are pun'tured at inter!als %y large

nu'lear pores, +hi'h transport mole'ules %et+een thenu'leus and the'ytosol# The nu'lear en!elope isdire'tly 'onne'ted to the e"tensi!e mem%ranes of theendoplasmi' reti'ulum#

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