Question

There is a Y chromosome gene in humans that has two alleles influencing hair growth on the pinna (external ear). One allele causes very hairy ears. The phenotypic effect of the other allele is to not have hairy ears. A man with hairy ears and a woman without hairy ears are starting a family. What is the probability their first child will be a girl with hairy ears

Answer 1

Answer:

Since the gene is located on the Y chromosome, and the Y chromosome is absent in females, the probability their first child will be a girl with hairy ears is zero

Explanation:

Y-linkage, also known as holandric inheritance is a form of sex linkage in which inherited traits in offsprings are produced by genes located on the Y chromosome. The Y chromosome is one of the sex-determining chromosomes and is present only in males. Males have a copy of the Y chromosome and an X chromosome while females have two copies of the X chromosome.

For a trait that is linked to the Ychromosome, the phenotypic effect occurs only in males and is always manifested in these males. Since the Y chromosome is absent in females, the character and its phenotypic effect are absent from daughters of trait carriers. Therefore, all daughters will be normal.

Since the gene for hair growth onnthe pinna is located on the Y chromosome, and the Y chromosome is absent in females, the probability their first child will be a girl with hairy ears is zero.

Answer 2

The probability that their first child will be a girl with hairy ears is zero.

The sex chromosomes in humans are the X and Y chromosomes. They determine the sex of a baby and also carry the sex linked traits. A baby girl results from XX  and a baby boy results from XY.

We are told that this gene for hairy ears is located on the Y chromosome. This chromosome is absent in a girl child. hence, the probability that their first child will be a girl with hairy ears is zero.

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