genetics

Assignment 3A

Part 1

Suppose two phenotypes- eye color and hair color- are due to simple dominant/recessive allele pairs for two independent genes. (this is not really true, but let’s use it for this practice). Brown hair is dominant to blond hair and brown eyes are dominant to blue eyes.

1. A couple who both have brown eyes and brown hair have a child who has blue eyes and brown hair.

What can you infer about the genotype of the child and the parents from this much information?

The child is:

homozygous dominant / heterozygous / homozygous recessive / can’t tell for the eye color gene

homozygous dominant / heterozygous / homozygous recessive / can’t tell for the hair color gene

The parents are both:

homozygous dominant / heterozygous / homozygous recessive / can’t tell for the eye color gene

homozygous dominant / heterozygous / homozygous recessive / can’t tell for the hair color gene

2. A couple who both have brown eyes and brown hair have a child who has brown eyes and blond hair.

What can you infer about the genotype of the child and the parents from this much information?

The child is:

homozygous dominant / heterozygous / homozygous recessive / can’t tell for the eye color gene

homozygous dominant / heterozygous / homozygous recessive / can’t tell for the hair color gene

The parents are both:

homozygous dominant / heterozygous / homozygous recessive / can’t tell for the eye color gene

homozygous dominant / heterozygous / homozygous recessive / can’t tell for the hair color gene

3. A couple who both have brown eyes and brown hair have a child who has blue eyes and blond hair.

What can you infer about the genotype of the child and the parents from this much information?

The child is:

homozygous dominant / heterozygous / homozygous recessive / can’t tell for the eye color gene

homozygous dominant / heterozygous / homozygous recessive / can’t tell for the hair color gene

The parents are both:

homozygous dominant / heterozygous / homozygous recessive / can’t tell for the eye color gene

homozygous dominant / heterozygous / homozygous recessive / can’t tell for the hair color gene

Consider just the parents in #3.

4. What is the chance that their next child will have blond hair and blue eyes?

5. What is the chance that their next child will have brown hair and blue eyes?

6. What is the chance that they will have a total of 3 children, all with blond hair and blue eyes?

7. What is the chance that they will have a child with brown hair and brown eyes, then a child with blond hair and brown eyes then a child with brown hair and blue eyes?

8. What is the chance that they will have three children, one each with brown hair and brown eyes, one with blond hair and brown eyes and one with brown hair and blue eyes?