34539.The human genes for colorblindness and for hemo-philia are both on the X chromosome, and theyshow a recombinant frequency of about 10 percent.Linkage of a pathological gene to a relatively harm-less one can be used for genetic prognosis. Shown be-low is part of a more extensive pedigree. Blackenedsymbols indicate that the subjects had hemophilia,and crosses indicate colorblindness. What informa-tion could be given to women III-4 and III-5 aboutthe likelihood of their having sons with hemophilia?(Problem 39 adapted from J. F. Crow,Genetics Notes: AnIntroduction to Genetics. Burgess, 1983.)40.A geneticist mapping the genes A,B,C,D, and Emakes two 3-point testcrosses. The ±rst cross of purelines isA/A?B/B?C/C?D/D?E/E3a/a?b/b?C/C?d/d?E/EThe geneticist crosses the F1with a recessive testerand classi±es the progeny by the gametic contribu-tion of the F1:A?B?C?D?E316a?b?C?d?E314A?B?C?d?E31a?b?C?D?E39A?b?C?d?E130a?B?C?D?E140A?b?C?D?E17a?B?C?d?E13100012345IIIIII
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