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

Well I hope you passed.

Answer 2

What is the phenotype of an XX individual that is alb-/alb+; doc-/ doc-? Select one sex and one color phenotype.

A. male
B. female
C. solid white fur
D. solid purple fur
E. patches of white & purple fur

Would an XXX smidget that is alb-/alb-/alb+ have more, less or the same amount of white fur as an XX smidget that is alb-/alb+?
A. More
B. less
C. same

Answer 3

The phenotype of an XXY smidget that is wild-type for both the alb and doc genes would be solid purple fur.

To understand why, let's break down the information given. The smidget's sex is determined by the presence or absence of a Y chromosome, just like humans. In this case, the XXY genotype indicates a male smidget.

The alb gene, present on the X chromosome, determines fur color. Individuals homozygous or hemizygous for a recessive, loss-of-function mutant allele (alb-/alb- or alb-/Y) will have white fur. However, an X-linked wild-type allele (alb+/X or alb+/Y) produces the normal fur color.

The doc gene, on the other hand, is not on the sex chromosomes and is autosomal. Its product is required for X-chromosome inactivation, which is a mechanism that balances gene dosage between males and females in mammals.

Since the XXY smidget is wild-type for both the alb and doc genes, it means that it carries at least one copy of the wild-type allele for alb. Therefore, it will have the normal fur color, which is solid purple.

Hence, the phenotype of an XXY smidget that is wild-type for both genes is a male smidget with solid purple fur.