Four eye-color mutants in Drosophila—apricot, brown, carnation, and purple—are inherited as recessive traits. Red is the dominant wild-type color of fruit-fly eyes. Eight crosses (A through H) are made between parents from pure-breeding lines.

Predict F₂ phenotype ratios of crosses A, B, D, and G. <>

A wild-type male and a wild-type female Drosophila with red eyes and full wings are crossed. Their progeny are shown below.

Males                                       Females                          _
3/8 full wing, red eye                 3/4 full wing, red eye
3/8 miniature wing, red eye.      1/4 purple eye, full wing
1/8 purple eye, full wing
1/8 miniature wing, purple eye

What is/are the genotype(s) of females with purple eye? Of males with purple eye and miniature wing?

A wild-type male and a wild-type female Drosophila with red eyes and full wings are crossed. Their progeny are shown below.

Males                                       Females                          _
3/8 full wing, red eye                 3/4 full wing, red eye
3/8 miniature wing, red eye.      1/4 purple eye, full wing
1/8 purple eye, full wing
1/8 miniature wing, purple eye

Using clearly defined allele symbols of your choice, give the genotype of each parent.

The gene causing Coffin–Lowry syndrome (OMIM 303600) was recently identified and mapped on the human X chromosome. Coffin–Lowry syndrome is a rare disorder affecting brain morphology and development. It also produces skeletal and growth abnormalities, as well as abnormalities of motor control. Coffin–Lowry syndrome affects males who inherit a mutation of the X-linked gene. Most carrier females show no symptoms of the disease but a few carriers do. These carrier females are always less severely affected than males. Offer an explanation for this finding.

Four eye-color mutants in Drosophila—apricot, brown, carnation, and purple—are inherited as recessive traits. Red is the dominant wild-type color of fruit-fly eyes. Eight crosses (A through H) are made between parents from pure-breeding lines.

Which of these eye-color mutants are X-linked recessive and which are autosomal recessive? Explain how you distinguish X-linked from autosomal heredity. <>

For each pedigree shown,

Identify which simple pattern of hereditary transmission (autosomal dominant, autosomal recessive, X-linked dominant, or X-linked recessive) is most likely to have occurred. Give genotypes for individuals involved in transmitting the trait. 

Figure 3.22 (page 120) illustrates reciprocal crosses involving chickens with sex-linked dominant barred mutation. For Cross A and for Cross B, cross the F₁ roosters and hens and predict the feather patterns of roosters and hens in the F₂.