Question

Red–green color blindness is an X-linked recessive trait in humans. Polydactyly (extra fingers and toes) is an autosomal dominant trait. Martha has normal fingers and toes and normal color vision. Her mother is normal in all respects, but her father is color blind and polydactylous. Bill is color blind and polydactylous. His mother has normal color vision and normal fingers and toes. If Bill and Martha marry, what proportions of children with specific phenotypes would they be expected to produce? The answers only include the proportions of some of the possible phenotypes; other phenotypes are also expected to occur but are not included.

Answer 1

Answer:

The girls with polydactyly  color-blind and is 1/8, the boys with normal fingers and color vision is 1/8.

Explanation:

X - linked recessive trait may be defined as the trait that are normally passes down from mother to son. Males have high chances since they have only one X chromosme. The female should have both X chromosome affected to express the trait. Autosomal dominant trait express the trait in both the homozygous dominant and heterozygous condition.

The red - green color blinded male with polydactylous is married with female that have normal color vision and normal toes and finger. With the help of pedigree chart and probability,the outcome of their children with specific phenotype can be calculated.

Martha is normal for poldactyly and contains recessive trait for polydactyly. She is a carrier for the color blindness as his father is affected by the disease. Bill is affected by the color blindness and heterozygous for the polydactyly trait. The marriage between marry and bill have the children with  1/8 proportion of the girls can be color bind and shows polydactyly {1/4 ( girls with color blindness) × 1/2 ( the probability of polydactyly}. 1/8 proportion of the boys with normal vision and normal toes and finger {1/4 (boys are normal) × 1/2 ( the probability of normal toes and finger}.