Chapter 14 HO

pgeneraon onlytwopossiblegametetypes f1generaon

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Unformatted text preview: *! Mendel studied UNLINKED GENES. Ques/on:$$Do!the!alleles!for!one!character!assort!into!gametes!dependently!or!independently!of! the!alleles!for!a!different!character?! INDEPENDENTLY!!!!!! P)Genera<on) Only!two!possible!gamete!types! F1)Genera<on) Hypothesis!of!dependent! assortment! Hypothesis!of!independent! assortment! Two!possible! gamete!types! Predic<ons:) Phenotypic ratio: Four!possible! gamete!types! 3:1 (dependent) Experimental)) 315 Round, Yellow Results:))) 108 Round, Green 101 Wrinkled, yellow 32 Wrinkled, green 9:3:3:1 (independent) If you divide all these numbers by 32, you get the ratio 9:3:3:1 !!!!! Mendel’s$second$law:$$Law$of$independent$assortment$ Each!pair!of!alleles!segregates!independently!of!each!other!pair!of!alleles!during!gamete! forma%on! Seed$Color$ F1:))Y)y))x!!Y)y!cross! Y! Predicted)Phenotypes:) ! y! ! Y!Y! y! ! R! ! Y!y! Egg! Egg! ! Y! ! Sperm! Seed$Shape$ F1:))R)r))x!!R)r!cross! Sperm! R! r! Y!y! y!y! R!R! R!r! ! r! ! R!r! rr! 3 Yellow (75%), 1 Green (25%) Combine$Phenotypes:$$mul/ply$individual$probabili/es$ Yellow!Round!=!!!!!!!!3/4!*!3/4!!=!9/16! ( Green!Round!=!!!!!!!!!25%) * (75%) = 3/16 9:3:3:1 ratio Yellow!Wrinkled!=!!!!3/4!*!1/4!=!3/16! Green!Wrinkled!=! !!(25%) * (25%) = 1/16 ! 3 round (75%), 1 wrinkled (25%) Laws$of$Probability$Govern$Mendelian$Inheritance$ Probabili<es)range)from)0)to)1) Event!certain!to!occur!has!a!probability!of!1! Event!that!is!certain!not!to!occur!has!a!probability!of!0! ! Coin)Toss:) Probability!of!heads!=!½! Probabilities of all possible outcomes for an event must add up to 1 Probability!of!tails!=!½! $ Each$coin$toss$is$an$independent$event$ $ What$is$the$probability$that$two$coins$will$both$land$heads?$ (1/2) $$$$$$$ * (1/2) = (1/4) --> 25% chance $$$$$$ QUESTION: Probability of flipping 2 coins at the same time and ONE is a tail and ONE is a head? 1/2 = 50% ! Similarly$the$alleles$for$one$gene$segregate$independent$of$the$alleles$for$another$gene$ Can$think$of$them$as$individual$events$ ! Calcula/ng$the$probability$of$specific$genotype$in$an$F2$offspring$:$$$ Seed$Color$ F1:!!Y)y!!x!!Y)y!cross! y! ! ! Egg! Y! ! ! y! Y!Y! ¼! Y!y! ¼! Y!y! ¼! y!y! ¼! F2:))) ¼)YY:))½)Yy:)¼)yy) ! ! R!R! R!r! ¼!! ¼!! ! !! rr! r! ! R!r! ¼!! ¼!! ! ! F2:)¼)RR:))½)Rr:))¼)rr) R! Egg! Y! Sperm! Seed$Shape$ F1:!!R)r!!x!!R)r!cross! Sperm! R! r! What$is$the$probability$of$a$F2$plant$having$the$following$ genotypes?$ ) YYRR!=! 1/16 --> (1/4)(1/4) !! Yyrr!=! !1/8 --> (1/2)(1/4) ! YyRr!=! !1/4 --> (1/2)(1/2) ! ! Mul/ply$individual$probabili/es$ Can!combine!these!mul%plica%on!and!addi%on!rules!to!predict!outcomes!of!more!complex! cros...
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