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Unformatted text preview: g the parental phenotypes) approach 50%, it is difficult to distinguish between independent assortment (interchromosomal recombination) and intrachromosomal recombination between two "linked" loci. This can be seen from the test cross data for the following three loci. A B a b x a b a b B C b c x b c b c BC bc Bc Linked or bC Unlinked?
47 Phenotypes Phenotypes 1159 1017 17 12 2205
March 19, 2012 AB 770 ab 716 Ab 401 nonparentals aB 318 2205 BIS101001, Spring 2012--Genes and Gene Expression, R.L. Rodriguez 2012 Chi-square test for linkage The likelihood of linkage can be tested using the Chi-square test (page 127). The test begins by making a hypothesis. For example:
q " The B, C loci are unlinked and located on the separate chromosomes." Next, the Chi-square formula is used to compare the observed number of progeny types to the expected number of progeny types, assuming independent assortment (1:1:1:1). 2 =
2 0 = observed progeny types E = expected progeny types based on the hypothesis = sum of calculations for each progeny types
March 19, 2012 BIS101001, Spring 2012--Genes and Gene Express...
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