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

A.Male
B.Female
C.solid white fur
D.solid purple fur
E.patches of white & purple fur

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

The phenotype of an XXY smidget that is wild-type for both of these genes would be:

B. Female

C. Solid white fur

To determine the phenotypes of the smidgets in each scenario, we need to understand the genetic background and the effects of different genes.

First, let's analyze the information given about the smidgets in the question.

1. The smidget has a sex determination system similar to humans, with the presence or absence of a Y chromosome determining male or female sex, respectively.

2. The smidget has only two of its thousands of genes located on the X chromosome.

3. The alb gene is located on the X chromosome and is responsible for fur color. Recessive, loss-of-function mutant alleles (alb-) result in white fur, while wild-type alleles (alb+) produce the expected color.

4. The doc gene is an autosomal gene involved in X-chromosome inactivation. It is required for the process of dosage compensation, which equalizes the expression of genes on the X chromosome between males and females.

Now let's answer each question step by step:

1. What is the phenotype of an XXY smidget that is wild-type for both alb and doc genes?

Since the smidget is XXY, it has two X chromosomes and lacks the Y chromosome required for male determination. Therefore, the genotype of this smidget is XXY, with wild-type alleles for both the alb and doc genes.

The XXY smidget will develop as a female because the presence of two X chromosomes overrides the absence of the Y chromosome. However, the dosage compensation mechanism regulated by the doc gene should still occur, leading to the normal dosage of gene expression.

As for fur color, the smidget has wild-type alleles for the alb gene. So, the color phenotype would be solid purple fur. Therefore, the correct answer is:

B. Female with solid purple fur

2. What is the phenotype of an XX individual that is alb-/alb+; doc-/doc-?

This individual is XX, meaning it has two X chromosomes and is expected to develop as a female. The genotype of this individual shows that it carries a loss-of-function mutant allele for the alb gene (alb-) and is heterozygous (alb+), resulting in patches of purple fur interspersed with patches of white.

Since the individual is doc-/doc-, it lacks the autosomal gene required for X-chromosome inactivation, which results in the absence of dosage compensation. Consequently, the patches of purple and white fur will be present as both X chromosomes contribute to fur color.

Therefore, the correct answer is:

B. Female with patches of white and purple fur

3. 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+?

An XX smidget with the genotype alb-/alb+ will have patches of white and purple fur, as explained in question 2.

Considering an XXX smidget has three X chromosomes, it means it has an extra copy of the alb+ allele, which produces the expected fur color. Since the alb- allele is recessive, the presence of the alb+ allele will mask its effects.

Therefore, an XXX smidget that is alb-/alb-/alb+ would have the same amount of white fur as an XX smidget that is alb-/alb+.

The correct answer is:

C. Same