Genetics: Analysis and Principles 5th Edition by Robert Brooker

Exercise 53

As mentioned in Experimental Question E12, red eyes is the wildtype phenotype in Drosophila , and several different genes (with each gene existing in two or more alleles) affect eye color. One allele causes purple eyes, and a different allele causes vermilion eyes. The purple and vermilion alleles are recessive compared with red eye color. The following crosses were made, and the following data were obtained:
Cross 1: Males with vermilion eyes × females with purple eyes
354 offspring, all with red eyes
Cross 2: Males with purple eyes × females with vermilion eyes
212 male offspring with vermilion eyes
221 female offspring with red eyes
Explain the pattern of inheritance based on these results. What additional crosses might you make to confirm your hypothesis
Experimental Question E12
In Drosophila, red eyes is the wild-type phenotype. Several different genes (with each gene existing in two or more alleles) are known to affect eye color. One allele causes purple eyes, and a different allele causes sepia eyes. Both of these alleles are recessive compared with red eye color. When flies with purple eyes were crossed to flies with sepia eyes, all of the F 1 offspring had red eyes. When the F 1 offspring were allowed to mate with each other, the following data were obtained:
146 purple eyes
151 sepia eyes
50 purplish sepia eyes
444 red eyes
Explain this pattern of inheritance. Conduct a chi square analysis to see if the experimental data fit your hypothesis.