13. Mendelian Genetics

What is indicated when a single-character testcross yields offspring that all have the dominant phenotype?

A gray-bodied, vestigial-winged fly is crossed with a black-bodied, normal-winged fly. The F₁ progeny is testcrossed. Among the resulting offspring, __________ is a parental type, and __________ is a recombinant type.

Two black female mice are crossed with a brown male. In several litters, female I produced 9 black offspring and 7 brown; female II produced 57 black offspring. What deductions can you make about the inheritance of black and brown coat color in mice? What are the genotypes of the parents?

In flies, small wings are recessive to normal wings. If a cross between two flies produces 8 small-wing offspring and 28 normal-wing offspring, what are the most likely genotypes of the parents? (Use S to represent the normal-wing allele and s to represent the short-wing allele.)

In flies, small wings are recessive to normal wings. If a cross between two flies produces 8 small-wing offspring and 28 normal-wing offspring, what are the most likely genotypes of the parents? (Use S to represent the normal-wing allele and s to represent the short-wing allele.)

The smooth feathers on the back of the neck in pigeons can be reversed by a mutation to produce a 'crested' appearance in which feathers form a distinctive spike at the back of the head. A pigeon breeder examined offspring produced by a single pair of non-crested birds and recorded the following: 22 non-crested and 7 crested. She then made a series of crosses using offspring from the first cross. When she crossed two of the crested birds, all 20 of the offspring were crested. When she crossed a non-crested bird with a crested bird, 7 offspring were non-crested and 6 were crested. For these three crosses, provide genotypes for parents and offspring that are consistent with these results.

In 1981, a stray black cat with unusual rounded, curled-back ears was adopted by a family in California. Hundreds of descendants of the cat have since been born, and cat fanciers hope to develop the curl cat into a show breed. Suppose you owned the first curl cat and wanted to develop a true-breeding variety. How would you determine whether the curl allele is dominant or recessive? How would you obtain true-breeding curl cats? How could you be sure they are true-breeding?

In 1981, a stray black cat with unusual rounded, curled-back ears was adopted by a family in Lakewood, California. Suppose you owned the first curl cat and wanted to breed it to develop a true-breeding variety. Describe tests that would determine whether the curl gene is dominant or recessive and whether it is autosomal or sex-linked. Explain why you think your tests would be conclusive. Describe a test to determine that a cat is true-breeding.

You have crossed two Drosophila melanogaster individuals that have long wings and red eyes—the wild-type phenotype. In the progeny, curved wings and lozenge eyes mutant phenotypes appear as follows: What is the genotype of the male parent?

You have crossed two Drosophila melanogaster individuals that have long wings and red eyes—the wild-type phenotype. In the progeny, curved wings and lozenge eyes mutant phenotypes appear as follows: What is the genotype of the female parent?