!Name!________________________________!!!!!!!BIO!2110!–!Genetics!!Exam!2!!4!November!2016!!!!calculators!are!permitted!!see!last!two!pages!for!potentially!useless!information!! !!!!!1.! In!cuttlefish,!allelic!variation!in!a!single!gene!results!in!variation!in!swimming!speed.!!Allelic!variation!in!a!linked!gene!results!in!variation!in!the!ability!of!cuttlefish!to!change!their!skin!color.!!Based!on!the!segregation!data!presented!below,!determine!the!recombination!frequency!between!these!genes.!![P0s!are!homozygous.]!!SHOW%YOUR%WORK!!P0!Fast,!Polychrome!x!Slow,!Monochrome!!!!↓ !F1!Fast,!Monochrome!x!Fast,!Monochrome!!!↓!!F2!Fast,!Monochrome!Fast,!Polychrome!Slow,!Monochrome!Slow,!Polychrome!!!4,125!!1,875!!1,875!! 125!!!! !2.! Below!are!shown!segregation!from!reciprocal!monohybrid!crosses!for!two!genes,!the!fat$head!gene!in!grasshoppers!and!the!tetrodotoxin!gene!pufferfish.!!For!each!of!these!genes,!explain!the!segregation!patterns!of!F1!and!F2!phenotypes.!![All!P0s!are!from!populations!that!are!fixed!for!either!the!dominant!or!recessive!allele.]!!reciprocal crosses for the fat head gene !cross 1 !cross 2 P0!♀ fat head !♂ thin head !♀ thin head !♂ fat head !!↓!!!!↓!!F1!♀ fat head !♂ fat head !♀ thin head !♂ thin head !!↓!!!!↓!!F2!♀ thin head ♀ fat head ♂ thin head ♂ fat head !! 156!! 0!! 153!! 0!!♀ thin head ♀ fat head ♂ thin head ♂ fat head !! 129!! 0!! 134!! 0!!!!!!!!!!reciprocal crosses for the tetrodotoxin !cross 1 !cross 2 P0!♀ toxic !♂ nontoxic !♀ nontoxic !♂ toxic !!↓!!!!↓!!F1!♀ toxic !♂ toxic !♀ toxic !♂ nontoxic !!↓!!!!↓!!F2!♀ toxic ♀ nontoxic ♂ toxic ♂ nontoxic !! 137!! 0!! 68!! 69!!♀ toxic ♀ nontoxic ♂ toxic ♂ nontoxic !! 53!! 47!! 49!! 51!!! !3.! In!octopi,!allelic!variation!in!the!tententacle!gene!results!in!variation!in!tentacle!number.!!Allelic!variation!in!the!fuscluster!gene!results!in!frequent!fusions!of!clusters!of!suckers!on!the!tentacles.!!Based!on!the!segregation!data!presented!below,!are!these!two!genes!linked?!![P0s!are!homozygous.]!!SHOW%YOUR%WORK%!P0!ten,!unfused!x!eight,!fused!!!!↓!!!F1!eight,!unfused!X!eight,!unfused!!!!↓!!!F2!eight,!unfused!ten,!unfused!eight,!fused!ten,!fused!!435!163!173!!!29!!! !4.! Meiotic!recombination!(crossover)!is!precise!to!the!base!pair.!!Explain,!based!on!the!molecular!mechanism!of!recombination,!how!such!precision!is!possible.!! !!5.! Based!on!the!test!cross!data!presented!below,!place!the!evrs,!to,!tnkr!and!chnc!genes!on!a!recombination!map!in!their!proper!order.!!IT!IS!NOT!NECESSARY!to!calculate!recombination!frequencies!between!these!genes.!!Progeny!genotypes!are!shown!only!for!the!chromosomes!derived!from!the!heterozygous!parent.!!Among!progeny,!reciprocal!genotypes!are!grouped!together.!!cross!1!!$evrs$$$$$tnkr$$$chnc$EVRS$TNKR$$CHNC$x!evrs$tnkr$chnc$evrs$tnkr$chnc$!!↓!!!EVRS$TNKR$$CHNC$evrs$$$$tnkr$$$$$$chnc$!315!315!!!!EVRS$$TNKR$$$chnc$evrs$$$tnkr$$$CHNC!!!!35!!!35!!!!EVRS$$$tnkr$$$$chnc$evrs$$$TNKR$$CHNC!!!!15!!!15!$!!EVRS$$tnkr$$$CHNC$evrs$$$TNKR$$$$chnc$!135!135!!!!cross!2!!$evrs$$$$$to$$$$tnkr$EVRS$$TO$$TNKR$x!evrs$$$$$to$$$$tnkr$evrs$$$$$to$$$$tnkr$!!↓!!!EVRS$$TO$$TNKR$evrs$$$$$to$$$$tnkr!!360!360!!!!EVRS$$$$TO$$$$$tnkr$evrs$$$$$to$$$$TNKR!!!!40!!!40!!!!EVRS$$$$to$$$$$$tnkr$evrs$$$$TO$$$$TNKR!!!!90!!!90!$!!EVRS$$to$$TNKR$evrs$$$$$TO$$$$tnkr$!!!10!!!10!!! !6.! Based!on!the!epistasis!data!presented!below,!construct!a!genetic!pathway!for!the!regulation!of!eye!number!in!Brachypelma.!!genotype!phenotype!single!mutants!!$sxorb$six!eyes!$hexocular$six!eyes!$decocular$ten!eyes!$xyes$ten!eyes!$teneye$ten!eyes!double!mutants!!$sxorb;$decocular$six!eyes!$sxorb;$xyes!ten!eyes!$sxorb;$teneye$six!eyes!$hexocular;$decocular$ten!eyes!$hexocular;$xyes$ten!eyes!$hexocular;$teneye$ten!eyes!!! !7.! Allelic!variation!in!a!single!gene!results!in!flower!color!variation!in!Laqueum$diaboli.!!Based!on!the!segregation!data!presented!below,!describe!the!dominance!relationships!for!the!alleles!of!this!gene.!![P0s!are!homozygous.]!!P0! ! purple!! x! white!!! ! ! ! ↓!!F1! ! pink! ! x! pink!!! ! ! ! ↓!!F2! ! purple!! 315!! ! pink! ! 627!! ! white! ! 312!!!!! !8.! In!Gavialis$gangeticus,!recessive!mutations!in!the!pink!gene!result!in!pink!teeth!(the!wild-type!tooth!color!is!white).!!Recessive!mutations!in!the!unlinked!toothless!gene!result!in!animals!without!teeth.!!From!the!dihybrid!cross!shown!below;!!!i.! what!phenotypes!would!be!observed!in!the!F2!generation?!!!ii.! out!of!800!F2s,!how!many!of!each!phenotype!would!be!expected?!iii.! briefly,!explain!how!you!determined!the!number!of!expected!animals!in!each!phenotypic!class.$![P0s!are!homozygous]!!P0!toothless!x!pink!teeth!!!!↓!!!F1!white!teeth!!white!teeth!!!!↓!!!!!F2!phenotypes!!number!expected!!!!!!!!!!!!!!!!!!!!! !9.! The!huey,!duey!and!louie!genes!all!are!on!the!same!chromosome!(see!below).!!huey!and!duey!are!separated!by!10!cM.!!duey!and!louie$are!separated!by!30!cM.!!Based!on!the!segregation!data!presented,!how!much,!if!any,!crossover!interference!is!present!in!this!region!of!this!chromosome?!!Progeny!genotypes!are!shown!only!for!chromosomes!derived!from!the!heterozygous!parent.!!Chromosomes!are!shown!in!reciprocal!pairs.!!SHOW%YOUR%WORK!!!!huey$$$$$duey$$$$louie$HUEY$DUEY$LOUIE$x!huey$$$$$duey$$$$louie$huey$$$$$duey$$$$louie$$!!↓!!!HUEY$DUEY$LOUIE$$huey$$$$duey$$$$louie$!!315!309!!!!HUEY$DUEY$$$louie$huey$$$duey$$LOUIE!!!!37!!!39!!!!HUEY$duey$$$$louie$$huey$$DUEY$LOUIE!!!!141!!!135!$!!HUEY$$duey$$LOUIE$huey$$DUEY$$$$louie$!!!11!!!13!!! !hueydueylouie10#cM################# # #################### # #################### 30# cM10.!Null!mutations!are!mutations!that!completely!eliminate!gene!function.!!In!some!genes,!null!mutations!are!dominant.!!Provide!a!biochemical!explanation!for!the!dominance!of!loss-of-function!mutations.!!! !!probability!df!0.90!0.50!0.20!0.05!0.01!0.001!1!0.02!0.46!1.64!3.84!6.64!10.83!2!0.21!1.39!3.22!5.99!9.21!13.82!3!0.58!2.37!4.64!7.82!11.35!16.27!4!1.06!3.36!5.99!9.49!13.28!18.47!5!1.61!4.35!7.29!11.07!15.09!20.52!!χ2!values!Lod!=!Log10(odds)! ! χ2!=!Σ![(obs-exp)2/exp]! ! p2!+!2pq!+!q2!=!1!p2!+!q2!+!r2!+!2pq!+!2pr!+!2qr!=!1! ! df!=!n!–!1!!!!!!!!! ¼!p2! !!!!!!!!!!p!+!q!=!1! ! ! #classes!=!2n!+!1! ! p!+!q!+!r!=!1! ! !parental!gamete!frequency!=!½!(1!–!p)! ! recombinant!gamete!frequency!=!½!p!! ! !Nt!=!N0!x!e-rt! ! r!=!ln[N(t2)/N(t1)]/(t2!-!t1)!!!!!!θT!=!π!