Name%______________________________%%%%%BIO%2110%-%Genetis%%Exam%1%%30%September%2016%%see%last%page%for%potentially%useless%information%Name%______________________________%% %Name%______________________________%1.% In%eukaryotic%cells,%what%happens%when%the%leading%strand%from%one%origin%of%replication%meets%the%lagging%strand%from%an%adjacent%origin%of%replication?% %Name%______________________________%2.% Below%is%a%diagram%of%a%eukaryotic%protein-coding%gene.%%Numbered%boxes%represent%exons.%%Jagged%lines%represent%introns.%%Start%(ATG)%and%stop%(TGA)%codons%of%the%open-reading%frame%are%indicated.%%Indicate%on%this%diagram%(as%precisely%as%possible)%the%positions%of:%%i. the%promoter%ii. the%polyA%addition%signal%iii. the%5’%UTR,%and%iv. the%3’%UTR%%v.% What%impact(s)%would%a%mutation%that%deleted%the%polyA%addition%signal%have%on%the%transcription%AND/OR%co-transcriptional%processing%of%RNA%from%this%gene?%%Explain%the%reasoning%behind%your%answer(s).%%%%%%%%%%% %ATG TGA123Name%______________________________%3.% Chromatin%structure%can%impact%gene%expression%(see%below).%%In%closed%chromatin,%genes%can%not%be%transcribed.%%In%open%chromatin,%genes%can%be%transcribed.%%Describe%a%transcriptional%regulatory%mechanism%that%can%convert%closed%chromatin%to%open%chromatin.%%[This%mechanism%includes%three%steps.%%Include%all%of%these%steps%in%your%answer.]%%%%% %Name%______________________________%4.% Below%is%a%diagram%of%a%eukaryotic%protein%coding%gene.%%Exons%(numbered%1%–%4)%are%shown%as%thick%horizontal%lines.%%Flanking%DNA%is%shown%as%thin%horizontal%lines.%%The%position%of%the%start%codon%in%exon%1%is%indicated%by%an%arrowhead.%%Below%this%diagram%is%a%partial%sequence%of%the%coding%strand%of%this%gene%that%includes%the%start%codon%and%that%spans%intron%1.%%Exonic%sequences%are%indicated%with%upper%case%letters.%%Intronic%sequences%are%indicated%with%lower%case%letters.%%%%AGTGAATGGTAAAGguaagtttcttctgatcattagatggactaccgatcagTTTACATTT %i. What%are%the%first%five%amino%acids%that%are%coded%for%in%this%gene?%%[Use%the%genetic%code%chart%included%on%the%last%page%of%this%exam.]%%ii.% Which%of%the%following%mutations%most%likely%would%have%a%deleterious%impact%on%the%function%of%this%gene?%%Explain%your%answer.%•%an%AàT%substitution%at%position%3%in%codon%two%•%deletion%of%all%three%nucleotides%of%codon%two%•%deletion%the%second%nucleotide%of%codon%two%% %1234Name%______________________________%5.% What%role%does%the%5’%cap%play%in%mRNA%stability%in%eukaryotic%mRNAs?%%What%roles%does%the%5’%cap%play%in%protein%synthesis%in%eukaryotic%cells?%%% %Name%______________________________%6.% What%is%the%“branch%point”%nucleotide%of%a%eukaryotic%intron?%%Where%is%the%branch%point%nucleotide%located?%%What%role%does%the%branch%point%nucleotide%play%in%the%splicing%of%introns?%%% %Name%______________________________%7.% In%the%nematode,%C.#elegans,%the%erztz%gene%is%expressed%in%the%excretory%gland%and%the%post-anal%gland%(see%below).%%This%expression%pattern%also%is%observed%in%GFP%reporter%genes%that%contain%5%kb%of%5’%flanking%DNA%(reporter%gene%A%below).%%Some%deletions%within%this%region%of%5’%flanking%DNA%(dotted%lines%in%C%–%D)%alter%this%expression%pattern.%%%%i.% Based%on%these%deletions,%circle%the%regions%of%5’%flanking%DNA%contain%enhancers%that%regulate%expression%in%the%excretory%(excr)%and/or%post-anal%(pag)%gland%(indicate%which%region%regulates%expression%in%which%gland).%%%ii.% Would%the%enhancers%in%these%regions%of%DNA%be%the%same%or%different?%%Explain%your%answer.%%iii.% Based%on%these%results,%how%must%the%cells%of%the%excretory%gland%differ%from%the%cells%of%the%anal%gland%in%regard%to%regulation%of%erztz%gene%transcription?%%%%%%%%% %excretory(glandpost-anal(glandGFPGFPGFPGFPA.B.C.D.excr- - pag+- - ++- - ++- - --- - +erztz-5'-5lanking-DNAName%______________________________%8.% Glutamine%(Gln)%is%coded%for%by%two%codons,%CAA%and%CAG.%%A%single%tRNA%with%an%anticodon%of%5’%UUG%3’%can%read%(translate)%both%of%these%codon.%%If%the%tRNAgln%anticodon%was%mutated%from%5’%UUG%3’%to%5’%GUG%3’:%%i.% Would%the%mutant%tRNA%be%charged%with%Gln%or%with%some%other%amino%acid?%%If%different,%which%other%amino%acid?%%Explain%your%answer%in%the%context%of%substrate%specificity%of%aminoacyl%tRNA%synthetases.%%ii.% Would%the%mutant%tRNA%still%be%able%to%read%CAA%and%CAG%codons?%%If%not,%which,%if%any,%codon(s)%would%the%mutant%tRNA%be%able%to%read?%%% %Name%______________________________%9.% Transcriptional%activators%have%two%distinct%functional%domains.%%What%are%the%functions%of%these%two%domains?%%% %Name%______________________________%10.%In%eukaryotic%protein%coding%genes,%the%stop%codon%always%is%in%the%last%exon.%%Provide%a%mechanistic%reason%to%explain%why%this%essential.%% %Name%______________________________%%
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