70Chapter 2 •Patterns of Inheritance45.Red hair runs in families, and the accompanying illustration shows a large pedigree for red hair.(Pedigree from W. R. Singleton and B. Ellis,Journal ofHeredity55, 1964, 261.)a.Does the inheritance pattern in this pedigree sug-gest that red hair could be caused by a dominant ora recessive allele of a gene that is inherited in a sim-ple Mendelian manner?b.Do you think that the red-hair allele is commonor rare in the population as a whole?46.When many families were tested for the ability totaste the chemical PTC, the matings were groupedinto three types and the progeny totaled, with theresults shown below:about doing this? Show not only which crosses tomake, but also how many progeny should be sam-pled in each case.48.We have dealt mainly with only two genes, but thesame principles hold for more than two genes. Con-sider the following cross:A/a;B/b;C/c;D/d;E/e±a/a;B/b;c/c;D/d;e/ea.What proportion of progeny will phenotypically
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