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Published byBetty Knight Modified over 8 years ago
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Chapter 10.2 – Punnett Squares I.Punnett Squares – a shorthand way of finding the expected proportions of possible genotypes in the offspring of a cross A.Monohybrid Cross - 1 trait 1.2 boxes tall by 2 boxes wide 2.each parent creates 2 kinds of gametes for 1 trait
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3.Example: tall plant (TT) x short plant (tt)T t t Possible Phenotypes: 100% Tall Possible Genotypes:100% Tt Tt
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B.Dihybrid Cross – 2 traits 1.4 boxes tall by 4 boxes wide 2.each parent creates 4 kinds of gametes for 2 traits 3.Example: Guinea pig alleles S = short hair, s = long hair B = black hair, b = brown hair 2 guinea pigs, each SsBb, are mated with each other
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Use F.O.I.L. to create 4 gamete choices F=First (2 different letters), O=Outer, I=Inner, L=Last S s B b Gamete choices:SB, Sb, sB, sb
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SB Sb sB sb SB Sb sB sb Possible Phenotypes: Short, Black Hair (S_B_)9/16 Short, Brown Hair (S_bb)3/16 Long, Black Hair (ssB_)3/16 Long, Brown Hair (ssbb)1/16 SSBBSSBbSsBBSsBb SSBbSSbbSsBbSsbb SsBBSsBbssBBssBb SsBbSsbbssBbssbb
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