BIOL 3301 - Genetics Ch14B - Translation and Mutation 08 St

8/18/2019 BIOL 3301 - Genetics Ch14B - Translation and Mutation 08 St

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Three Steps of Translation

• Initiation

• Elongation

• Termination


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Stages of translation

• Initiation – _______________________________

– prokaryotes: mRNA Shine-Delgarno seqen!e "hi!h hy#rogen $on#s"ith rRNA

• ekaryotes: ri$osome atta!hes to %& !ap

– tRNAmet $in#s to ______________ • N-formylmethionine se# in prokaryotes' tRNAf (et' later remo)e#

• Initiation fa!tors

• Elongation: se of elongation fa!tors an# *T+

• Termination – ri$osome pases at ___________________

– release fa!tor $in#s' !omple, #isso!iates


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Translation Initiation

• Initiation reqirements:

– mRNA mole!le

– ______________________

– Initiator tRNA

– Three initiation fa!tors

– *T+

– (g-.


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Initiation• Small ri$osomal s$nit $in#s to

_______________________________________

• This !omple, $in#s to mRNA

• In prokaryotes initiation !o#on _____________ !alls for

f-met /N-formylmethionine0

• Shine-Dalgarno seqen!e A**A** pre!e#es start!o#on in mRNA1 !omplementary seqen!e on 2&of 34SrRNA –

________________________________________ • Initiation protein enhan!es $in#ing of f-met tRNA to the

small s$nit – sets the rea#ing frame – initiation!omple,


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AGGAGGU AUG

Ri$osome

$in#ing site

Initiation

!o#on

5’ 3’

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TRANSLATION INITIATION:

Bacteria

Translation fa!tors:

-initiation fa!tors /I6-3' I6-' I6-20

-elongation fa!tors /E6-T' E6-Ts'E6-*0-release fa!tors /R6-3' R6-' R6-20

-ri$osome re!y!ling fa!tor /RR60


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Initiation 7omple,

• 25S small s$nit $in#s _____________________

• 25S .I6s $in#s to mRNA A8* !o#on region – A seqen!e pstream of A8* is ne!essary' -9-35

position

– %&en# of %&8TR – ri$osome-$in#ing site RS/Shine-Delgarno seqen!e A**A* –prine-ri!h' !omplementary to 877877 pyrimi#ine – ri!h region at 2&-en# of 34S rRNA0


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Initiation 7omple,

• Initiator tRNA $in#s to A8* start !o#on

– Initiator f(et

• (ethionyl-tRNA synthetase a## methionine to

tRNA

• Transformylase a##s formyl grop to methionine

– f(et-tRNA;f(et


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Initiation 7omple,

• f(et-tRNA $in#s to A8* of 25S-mRNA !omple,'I62 is release#

• %5S s$nit $in#s – *T+ hy#rolysis

– I63' I6 release#

• 6inal !omple, –


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Translation Initiation In a!teria


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12/35PowerPoint ® Layered Art


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Elongation In +rokaryotes

• Anti!o#on of f(et-tRNA is hy#rogen-$on#e# to

A8* in + site

• Ne,t !o#on is in A site

• 7omplementary tRNA $in#s to A site

• tRNA is $on# to protein elongator fa!tor E6-T

• aa-tRNA $in#s to A site' *T+ hy#rolysis' ________________________________________


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Elongation

• Aminoa!yl tRNA $in#s to A site

• *ro"ing !hain of polypepti#e is transferre# from

tRNA in + site to tRNA in A site $y forming a ne" pepti#e $on#

• Ri$osome translo!ate along mRNA to position

ne,t !o#on against A site

• tRNA translo!ate from A-+ to +-E sites

• Elongation fa!tor E6-T•*T+ pro)i#e energy


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Translo!ation

• Ri$osome mo)es one !o#on to"ar#s __________

• Reqire a!ti)ity of protein elongation fa!tor E6-*

• E6-*-*T+ $in#s to the ri$osome' *T+ is hy#roly>e#• 8n!harge# tRNA is #ispla!e# a"ay from + site'

$in#s to E site' $lo!ks neat aa-tRNA from $in#ing toA-site ntil translo!ation is !omplete an# pepti#yl-

tRNA is $on# in + site• After translo!ation

– E6-* is release# sing *T+ hy#rolysis an# re!y!le#


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Termination

• 7hain-termination !o#ons 8AA' 8A*' 8*A enter Asite

• Re!ogni>e# $y release fa!tors R6s /Rf3 an# Rf1 only

one in ekaryotes eR60• +resen!e of release fa!tor !ases the a!ti)ity !hange

of pepti#yl transferase' a## "ater to !ar$o,yl of polypepti#e !hain

• Rea!tion releases polypepti#e from tRNA in the + site• 6ree tRNA mo)es to E site' mRNA release#' ri$osome

#isso!iate


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Termination

• '

– Ri$osome Re!y!ling 6a!tor

– Elongation 6a!tor * /E6-*0• fn!tion to release mRNA an# tRNAs from

ri$osomes an# #isso!iate the


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Termination

• I6-2 also helps the ri$osome-re!y!ling pro!ess $y !on)erting transiently

#isso!iate# s$nits into sta$le ones $y $in#ing to ________________________;

• This ?re!y!les? the ri$osomes for a##itionalron#s of translation


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PowerPoint ® Layered Art


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Ri$o>ymes

• A !atalyti! RNA – RNA en>yme

• 34S rRNA – !atalysis of pepti#e $on#

• Release fa!tor – RNA mole!le similar totRNA

• Ri$on!lease + - that !lea)es the hea# /%@0

en# of the pre!rsors of transfer RNA/tRNA0 mole!les

• snRN+s


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Translation In Ekaryotes

• tRNAi(et . I6----- + site #ire!tly

• %&!ap $in#ing protein 7+ /part of eI6-6 initiation

!omple,0 $in#s to


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Translation In Ekaryotes

• 95S initiation !omple, "ith (et-tRNA

$on# to mRNA "ith A8* in + site

• polyA tail is $on# $y poly/A0$in#ing

protein /+A+0' $in#s to eI6-*

• Initiation of translation is stimlate#


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Intera!tion of 2@ an# %@ en#s of mRNA

important in initiation of translation;


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Translation

• +rokaryotes – ri$osomes are smaller

– translation is !ople# to

trans!ription – more than one gene may $e

translate# from the same

mRNA

– translation is poly!istroni!

– the Shine-Delgarno seqen!ealigns mRNA on ri$osome

– the first amino a!i#

in!orporate# is N-

formylmethionine

• Ekaryotes – translation mono!istroni!

– ri$osomes re!ogni>e

mRNA $y $in#ing to


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(tations


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(tations

• 7hange in geneti! material -a mtation is an

________________________________;

• Sor!e of geneti! )aria$ility

• No)el phenotype ___________________


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(tations

• 7hange in !hromosome ________________

• 7hange in !hromosome ________________

• 7hange in the str!tre of in#i)i#al gene

– _________________________


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(tations

• Somati! or germinal

• Spontaneos or in#!e#

• Re)ersi$le

• *ain of fn!tion' loss of fn!tion' netral


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+oint (tations

• A##ition

• Deletion

• S$stittion

• 6rame-shift – (issense

– Nonsense – Netral

– silent

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BIOL 3301 - Genetics Ch14B - Translation and Mutation 08 St