Sex-linked Inheritance

1. What is an autosome?

2. How many pairs of autosomes does a human cell have?

3. How many pairs of sex chromosomes do humans cell have? What are the female sex chromosomes? What are the male chromosomes?

4. What is the probability of a man and his wife having a baby girl? Create a Punnett Square for proof.

5. Which parent determines the sex of the offspring? How do you know?

6. What is meant by a sex-linked characteristic?

7. Why is a pure red-eyed female fly represented as X^RX^R and a red-eyed male as X^RY?

Note: This information applies to questions 8-10.

In fruit flies, eye color is a sex-linked trait. The gene for red eyes is dominant to the gene for white eyes.

8. A white-eyed female fly is crossed with a red-eyed male.
1. What is (are) the genotype(s) of the F₁ females?

2. What is (are) are the genotypes of the F₁ males?

3. What would be the phenotype of all offspring?

9. Determine the probable genotypic and phenotypic ratios expected from a cross between:
1. A carrier (heterozygous) red-eyed female and a red-eyed male

2. A carrier female and a white-eyed male.