Genetics 311, Practice problem set 1.

1) Black coat color is a dominant trait in guinea pigs.  A black female guinea pig was testcrossed and produced 6 offspring, all black.  What is her probable genotype?  With what degree of confidence can her genotype be specified?

Answer: There's a 98.4% chance that she's BB.

2) Shorthorn cattle with the genotype CRCR are red, cattle with the CWCW genotype are white, and CRCW cattle are "roan."  If roan cattle show 35% of the coloration of red cattle, and white are essentially colorless,what is the degree of dominance?  Which allele is dominant?

Answer: CW (white) is dominant, D = 0.3

3) Homozygote TMTM individuals are said to have "thalassemia major" and generally die in childhood of severe anemia.  Heterozygotes TMTN have "thalassemia minor," a mild anemia, and generally survive.  What fraction of the adult offspring of two parents with thalassemia minor are expected to be anemic?

Answer: 2/3

4) Vestigial wings and ebony body color result from independently-assorting recessive mutations in Drosophila.  If a pair of VvEe flies are mated and produce 256 progeny, how many are expected to show ebony body color and normal wings?

Answer: 48

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