The smidget is a tiny mammal whose sex (like humans) is determined by the presence/absence of a Y chromosome and whose dosage compensation mechanism is just like humans as well. But, this mammal differs from humans in having only two of its thousands of genes on its X chromosome. One of the two genes is called alb. Individuals hemizygous or homozygous for a recessive, loss-of-function mutant allele are white furred, while alb-/alb+ heterozygotes have patches of purple fur interspersed with patches of white. The product of an autosomal gene, called doc, is required for X-chromosome inactivation. What is the phenotype of an XXY smidget that is wild-type for both of these genes? Select one sex and one color phenotype

Question

The smidget is a tiny mammal whose sex (like humans) is determined by the presence/absence of a Y chromosome and whose dosage compensation mechanism is just like humans as well. But, this mammal differs from humans in having only two of its thousands of genes on its X chromosome. One of the two genes is called alb. Individuals hemizygous or homozygous for a recessive, loss-of-function mutant allele are white furred, while alb-/alb+ heterozygotes have patches of purple fur interspersed with patches of white. The product of an autosomal gene, called doc, is required for X-chromosome inactivation. What is the phenotype of an XXY smidget that is wild-type for both of these genes? Select one sex and one color phenotype

Male
Female
solid white fur
solid purple fur
patches of white & purple fur

Answer 1

To determine the phenotype of an XXY smidget that is wild-type for both genes, we need to understand the effects of each gene on the fur color.

According to the information provided, the gene alb plays a role in fur color. Homozygous or hemizygous individuals for a recessive alb mutant allele have white fur, while heterozygotes (alb-/alb+) have patches of purple fur interspersed with patches of white.

The gene doc, on the other hand, is an autosomal gene that is required for X-chromosome inactivation. It is not directly involved in determining fur color but is relevant for the dosage compensation mechanism.

Given that an XXY smidget has an extra X chromosome, it means it has two X chromosomes and one Y chromosome. However, the question mentions that the smidget's sex, like humans, is determined by the presence or absence of a Y chromosome. In humans, individuals with two X chromosomes and one Y chromosome are typically male.

Taking all this information into account, the phenotype of an XXY smidget that is wild-type for both genes would be a male with patches of purple fur interspersed with patches of white.