Meosis Notes
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Transcript of Meosis Notes
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7/26/2019 Meosis Notes
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meiosis
Sunday, October 11, 2015
10:18 PM
Sexual reproduction
Sexual or asexual
Sexual reproduction
2 parents of opposite sex
Combination of enes from bot! parents
"!ere miosis comes in
#o come in
$ormation of ametes % come in to form &yote and !a'e ne( indi'idual
)sexual %
*n'ol'es sinle parent
O+sprin produced by mitosis % identical to parent
Many species do bot!
Some species ust do asexual
Some do asexual some of time and sexual at ot!er times
*n !ydra % oranism % celentarate
Cell % budd o+ of main body and form brand ne( little !ydra
-eetati'e % 'ery common in plants
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Send out runners % ne( plantlet
.o( an o+sprin % enetically identical to main plant
)nd se'ered and o+sprin free li'in
)lready tal/ed about mitosis
Miosis % sexual reproduction
Meiosis % in'ol'ed in sexual reproduction
Produces amete cells in'ol'ed in sexual reproduction
amete cells % !aploid % !alf amount of c!romosomes
aploid made in particular part of pody called erm cells
erm cells found in particular parts of body suc! as onands % testies and o'eries ofanimals
)nd in plants
*n !umanes % ametes made in testies
Called sperm and rest of structures % deli'ery system to et sperm to e %structures do ot!er t!ins as (ell
*n female % es produced in o'aries
)nd ettin sperm to es and &yote ettin formed % place (!ere to ro(
amete producin structures in plants
$lo(erin plants
Structures produce amets
o'ary at base of 3o(er
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O'ary % contains o'ules
4ui'alent of es in animal
Particular plant
Separate structure % ma/e male amets
)nt!er 6(!ere sperm oriinate7
Pollon eui'alent to animal sperm
Meiosis o'er'ie(
Main ob of meiosis % produce !aploid cells
alf number of c!romosomes as oriinal cell
.ot randomly c!osen !alf of c!romosomes
4ac! amete % one representati'e of eac! !omoloous of eac! c!romosomes
*n red to emp!asise importants
4ac! amete !as one representati'e of eac! !omoloous pair of c!romosomes
4xtra set at end % determines male or female
4ac! !omoloous pair
2 pairs of !omoloous c!romosomes
Pair number 1
4ac! x y structure
amete 1 of t!ose t(o
9oesnt matter (!ic! one
;ut one and only one
Pair number 2 % one of t!ose structures
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Same for all of t!em
eneral purpose of meiosis % amete cell t!at !as !alf of oriinal cell
alf of oriinal cell
Maintain a constant amount of enetic information
*f (e didnt do meiosis
Produced t!ins (e call ametes by mitosis
amete cell from one parent to anot!er parent
C!romosome % double
4ac! eneration double until cell c!o/ed (it! c!romosome
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>i/e mitosis except
#!ere are 2 cell di'isions
Meiosis 1 and meiosis ii
)nd !omoloous c!romosoems are separated
.atural (orld %
Meiosis % more li/e mitosis (it! extra t!ins
$irst t!in
C!romosomes duplicated
.ot ma/e lot of sence
"!y duplicate (!en oal is to cut in !alf
)s (ell see (it! e'olutionary /inds of t!ins
.ot al(ays most e?cient
;ut e'olution ta/es preexistin systems and modi@es to produce ne( /inds oft!ins
Meiosis % t!ins !appenin li/e mitosis % some c!anes
1 9uplicatin c!romosomes2 omoloues pair up 6synapsis 7 Meisis 1 % metap!ase % ri!t up next to eac! ot!er % one oes to one side one
oes to t!e ot!er % separate ot!ersA Separate c!romatids 6meiosis **7 % still !a'e c!romosomes in duplicated
condition % separate t!em
#(oB 9uplicate c!romosomes
Cell di'ision 1 % do is separate !omoloues % still left (it! c!romosomes induplicated condition
)not!er meiosis to separate sister c!romatids
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s!aped structure
#(o !omolous c!romosomes
s!aped on top in li!t blue
One !omoloous already duplicated
Dnderneat! it ot!er !omoloue t!at oes (it! it, also duplicated
#(o e'ents of miosis
)lready duplicated and !omoloous pairin up and comin toet!er
.ext e'ent
Separate from eac! ot!er
#(o !omoloous c!romosomes
Separated
Meiosis 2
One !omoloous c!romosomes
Still duplicated condition
a'e to separate sister c!romatids
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Separate sister c!romatids
4'ent ta/es place in second cell di'ision miosis 2
Meiosis 1
same p!ases as mitosis
Prop!ase % uniue t!in % !omoloous c!romosomes pair up
Pair li/e t!at synapsis comin toet!er
Metap!ase % pairs of !omoloues line up on euator
)nap!ase and telop!ase
omoloous c!romosomes mo'e to opposite poles
"!ic! !omoloue ends up at (!ic! pole is random
>ine up at euator
Sometimes mot!er on left side
Sometimes mot!er on ri!t side
Eandom
omoloues separate
*n anap!ase and telop!ase
et all !omoloues from fat!er oin one side and from mot!er oin to oneside
Eandom mix of t(o
Montra !olds
4ac! of ne( cells only !a'e one representati'e from !eac! !omoloous pair
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One t!in see !appenin
omoloous pairs linin up next to eac! ot!er
9o more t!an t!is
Crossin o'er t!at !appens (!en t!ey line up next to eac! ot!er
Synapsis
Metap!ase % meiosis 1
Pairs lined up toet!er on euator of cell
*n box % 1 !omoloue and bottom you see ot!er !omoloue
*n anap!ase and telop!ase
C!romosomes separated
#elop!ase % top portion of cell % one representati'e from one !omoloous pair
Eesults so far
Meiosis 1
2 cells % eac! represantati'e of eac! !omoloous pair
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;ut c!romosomes still duplicated state
One more cell di'ision to separate duplicated to sister c!romatids
Metap!ase
4ac! c!romosome is attac!ed at t!e euator
)nap!ase and telop!ase
Sister c!romatid separate
C!romosomes already duplicated
4nd of meiosis 1
2 cells
*n beinnin 2 cells
One representati'e
One pair of c!romosomes
$airly lare
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One on ri!t
)not!er pair % /inda small side
4ac! cells !a'e one bi and one smaller c!romosome
4ac! cells !a'e to undero anot!er cell di'ision
$ocus on eit!er one of !ese
Cell on top % cell oes t!rou! metap!ase
#(o c!romosomes line up on euator of cell
)nap!ase and telop!ase % separated into sister c!romatids
Meiosis ii
Eesults % A cells % eac! (it! t!e !aploid number of c!romosomes
4ac! amete !as one representati'e of eac! !omoloous pair
Ot!er aspects of meiosis
Male and female animals % di+er a little bit
Male amete formation % A sperm % oriinal and et A sperm
4 formation same (ould be true % A e cells
et A cells but one becomes e
ot!er cells produced are called polar bodies
.ot functional ametes
"!y t!at s!ould be case
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Sinle cell % underoes @rst biotic de'ision
Producin 2 cells and 2 cells producin A cells % A sperm cells
4 formation
Sinle cell
;ecomes t(o cells
)nd eac! becomes t(o cells
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Only one becomes e or o'um
Eemainin % dont act as ametes at all
Eeason (!y t!ree of t!ese are t!ro(n a(ay and not used
One of t!ins you s!ould be t!in/in of
4 compared to sperm % 'ery lare
*mportant for an e to !a'e a lot of material inside it
Pro'idin nutrition for de'elopin embryo
9iaram % cyto/enisis
9i'ides contents of cell % uneual in e formation
$irst di'ision (e et
Cell on top % a lot smaller t!an cell on bottom
*n next di'ision
Still discrepency
One larer t!an ot!er
Consolidatin all cytoplasmic material and in one iant cell and muc! smallercells discarded
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Dltimate purpose % ametes (it! enetic 'ariability
See !o( t!is can !appen
One t!ins t!at occurs
*ndependent assortment
Cell at top of diaram
Cell t!at !as F c!romosomes
pairs of !omoloous c!romosomes
One pair seem to be larest
One to left see smallest ri!t see someti!n in middle
pairs
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omoloous pairs come toet!er
>ine up on euator
)nd (ill mo'e to opposite poles of cell
ere (e color code c!romosomes
#o /eep trac/ of t!em
9ar/ blue on bottom % from fat!er
>i!ter blue % from mot!er
Mot!er c!romosome on top
)nd fat!er on bottom
One possible con@uration
)nd it does occur
ametes
One representati'e
One bi, one small, and one medium
#(o ametes produce
One (ill !a'e all mom
)nd ot!er (ill !a'e all dad
;ut (!en !omoloous c!romosomes come toet!er
>ots of ot!er posiblities too
.ext cell s!o(s anot!er one
One of dad on top and t(o of moms
i'e us di+erent ametes
amete one !a'e small c!romosome from fat!er and lare and medium fromfat!er and complementary opposite
ametes di+erent t!an oens abo'e
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enes on mot!er are di+erent t!an fat!er c!romosome
.ot completely di+erent
;ut !a'in 'ariation
Mot!er and fat!er bot! !a'e enes for eye color
Mot!er may !a'e blue eyes and fat!er may !a'e bro(n eyes
ametes 'ery di+erent from eac! ot!er
Same enes but alials may be di+erent
*ndependent assortment
One representati'e of eac! pair of !omoloues c!osen at random
Possible combinations
F c!romosomes pairs 2 to po(er G 8
umans 2 pairs 2 to 2 po(er 8 million res!uHes enetic material
8 di+erent possible ametes t!at come out of t!at
8 di+erent combinations
umans % 2 pairs
"ay to @ure out
2 to 2rd po(er
8 million di+erent combinations of mom and dad c!romosomes in ametes of!uman beins
) lot of enetic 'ariation
Ees!uHes
Ees!uHe enetic material
-ery important (!en (e tal/ about e'oltuion
4'olution % 'ariation
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#al/ about t!at %
#!is diaram on left
Pair of !omolous c!romosomes % dar/ blue and li!ter blue
Prop!ase %
Pair up toet!er in synapsis
*nterestin ioned toet!er
4xc!ane c!romosonal material
Crossin o'er
Called because in second picture
9ar/ blue % arm % dar/ to li!t
Crossin o'er toet!er
$ormation /yasmada
Cross eac! ot!er
"!at !appens
>ast t(o pictures
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4xc!ane of enetic information
)rm of li!t blue % attac!ed to dar/ blue and arm of dar/ blue attac!ed to li!tblue c!romosome
)t end % (e !a'e a c!romosome
More speci@cally c!romatid
Picture on left % portion of c!romosome of dar/ and li!t blue
C!romosome to ri!t
C!romatid % portion li!t blue and portion t!as dar/ blue
omoloous one from fat!er and one from mot!er
)ll c!romosome information s!uHed furt!er
$at!er oined (it! mot!er recirpical cross oin (it! mot!er
Crossin o'er
Occurs (!ile !omoloues are in synapsis
4ui'alent portions are exc!aned
Eesults in ne( enetic combinations
$urt!er s!uHin enetic material
.e( enetic combination
) lot due to independent
)nd no( youo et e'en more
enetic combination di+erent
9i+erent combinations of enetic 'arience put toet!er in di+erent (ays
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;efore % independent assortment 8 million combinations
.o( because of corssin o'er
.umber of combinations of dad and mom c!romosomal material is almostin@nite
enetic 'ariability and sexual reproduction
"!y are o+sprin from sexual reproduction di+erent from eac! ot!er
;ecause of
*ndependent assortment 6eac! amete ets a random representati'e of eac!!omoloous pair of c!romosomes7
Crossin o'er
Eandom pairin of ametes from mom 6e7 and dad 6sperm7 at fertili&ation
Pool of ametes by dad and mom
Put t(o toet!er form indi'idual
C!ances of reac!in into sperm pool and e pool and by c!ance % t(oametes same
*dentical t(in
.ot part of t(innin process
Odds are 0
So many possible combinations
Only (ay % sinle fertali&ed e % oes initial clea'ae and t!ose cells o on to
ma/e indi'iduals
Meiosis summery
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ametes
4ac! c!romosome duplicated durin interp!ase
;ein (it! duplicated c!romosome
#a/e loo/ at picture
>eft erm cell form male
Ei!t erm cell from female
4ac! cells !a'e one pair of !omoloous c!romosome
Simple cell
4ac! c!romosome duplicated
$ollo( one of t!ese meiosis processes
One on left
#(o x s!aped structures
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9uplicated condition
Miosis 1
#(o !omoloous pair up on euator of cell and oin to separate at end ofmeisis one 2 cells eac! !as one representati'e of !omoloous c!romosomes
#a/e t!ose cells
Contain duplicate state
Sister c!romatids separated
et t(o ne( cells
4ac! !as one sister c!romatid
A amete cells
4ac! !as one c!romosone
#op of diaram % oriinal cell 2 c!romosomes
One amete formed by mot!er and one formed by fat!er
)nd put t!em toet!er fertali&ed cell called &yote
9iploid number restored at fertili&ation