Chapter 14 HO

y sperm y yy yy yy yy f212

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Unformatted text preview: ses! ! #!of!gamete!types!=!2n;!n=#!of!characters! Trihybrid$Cross:$$$$ $ $$$$$$PpYyRr)))x))Ppyyrr) 23!=!8!gamete!types!–!huge!cross!! ! p! ! P!P! ¼! P!p! ¼! Pp! ¼! p!p! ¼! F2:)¼)PP:))½)Pp:)¼)pp) ! y! ! ! y! ! Sperm! y! Y!y! ¼! y!y! ¼! Yy! ¼! y!y! ¼! )F2:)))1/2 Yy, 1/2 yy ) R! Sperm! r! ! r! ! Egg! Egg! ! P! ! Y! p! Egg! P! Sperm! R!r! r!r! ¼!! ¼!! ! !! rr! r! ! R!r! ¼!! ¼!! ! ! 1 F2:) ))/2 Rr, 1/2 rr What$frac/on$of$the$offspring$from$this$cross$would$be$predicted$to$exhibit$the$recessive$ phenotypes$for$at$least$two$of$these$three$characters?$ ! !ppyyRr ! (1/4) * (1/2) !* (1/2) = 1/16 !! ! !ppYyrr !1/4!*!1/2!*!1/2!!=!1/16! ! !Ppyyrr !!(1/2) * (1/2) * (1/2) = 1/8 ! !PPyyrr !1/4!*!1/2!*!1/2!!=!1/16! ! !ppyyrr! !1/4!*!1/2!*!1/2!!=!1/16! Frac/on$of$offspring$with$$at$least$two$recessive$traits$ 6/16 --> 3/8 Extending$Mendelian$Gene/cs$for$a$Single$Gene$ ! Inheritance!of!characters!determined!by!a!single!gene!deviates!from!simple!Mendelian! paderns!when:! Alleles!are!not!completely!dominant!or!recessive! *! When a particular gene has more than two alleles When!a!single!gene!produces!mul<ple!phenotypes! ! 1.$$Incomplete$Dominance:$$When!neither!allele!for!a!gene!is!completely!dominant! Is$this$evidence$for$the$Blending$Hypothesis?$ ! No not enough you'd have to do another generation cross… but if you're right, you'd never see the parent alleles again… Incomplete --- BLENDING. F1!hybrids!have!a!phenotype!somewhat!between!the!parental!phenotypes! Set$up$an$F1$X$F1$cross$ WE SEE WHITE AND RED PHENOTYPES!!! Which means Blending hypothesis is WRONG. PARTICULATE HYPOTHESIS is right. Phenotypes:)!!! red: !2 pink: 1 white ! 1 ! !Genotype:!!!1!CRCR;!2CRCW;!1!CWCW! What$can$you$conclude$from$these$results?$ ! Segregation of the red allele from the white allele in the gametes produced by the pink parent supports PARTICULATE HYPOTHESIS. 2.  Codominance:!!Both!alleles!affect!the!phenotype!but!in!separate!dis%nguishable!ways! Example:!!MN!blood!group!V!dis%nct!from!the!beder!known!ABO!blood!groups! ! ! M!allele!codes!for!M!type!glycoprotein!on!the!surface!of!a!RBC! M! ! RBC! ! N!allele!codes!for!a!N!type!glycoprotein!on!the!surface!of!a!RBC! RBC! N! Predic<on:) M! M! N! MM! MN! Results:) CO-DOMINANT….both alleles are expressed! ! M! M! RBC! N! N! RBC! RBC! RBC! N! MN! M! N! NN! Genotype:! 1 MM: 2 MN: 1 NN !!Both!alleles!are!expressed!! ! !!Even!when!only!one!copy!is!present! For$any$character,$the$observed$dominant/recessive$rela/onship$of$alleles$depends$on$the$ level$at$which$we$examine$the$phenotype$ ! Example:!!TayVSachs!Disease!! (similar to POMPE disease) ! A!fatal!gene%c!disorder!caused!by!the!build!up!of!a!harmf...
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This document was uploaded on 02/04/2014.

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