F13 lecture 2 v2

Division b a a b a a b 4n b b a b b a b b or a b

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Unformatted text preview: forma7on not random with respect to some genes •  When calcula7ng genotype/phenotypes in a human- controlled cross the problem with dominance •  DD and Dd have the same phenotype = can’t tell them apart •  need to do a test cross to a homozygous recessive individual dd (short) –  D? x dd •  if DD, then genotype ra7o = 100% Dd, phenotype ra7o = 100% tall •  if Dd, then genotype ra7o = 50% Dd, 50% dd, phenotype ra7o = 50% tall, 50% short in class exercise 1 •  What if a gene H had two alleles with intermediate dominance, also called addi7ve effects, such that: –  HH = tall –  Hh = intermediate height –  hh = short •  do a PunneR square to determine the genotypic and phenotypic ra7os of a monohybrid cross th postulate Mendel’s 4 •  Independent assortment – alleles at different loci segregate independently of each other •  Mendel’s loci – were all unlinked – not close to each other on the same chromosome –  alleles at linked loci do not segregate independently – see future lecture Independent Assortment two loci illustrated on two different chromosomes (in this case, A/a; B/b...
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This document was uploaded on 02/27/2014.

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