bio-anth

Name: ______________________

Practice Problems in Mendelian Genetics

Use this sheet to work through each problem (or complete them on another piece of paper if you need more room).

1. People that have green, brown, and hazel eyes are considered pigmented (P) (dominant trait), whereas people who have grey or blue eyes are considered non-pigmented (p) (recessive trait).

Ask (or look at) 10 people (friends, family members, celebrities, etc.) and write down their phenotype (pigmented or non-pigmented, and then write down all possible genotypes).

Individual	Phenotype	Genotype(s)
1
2
3
4
5
6
7
8
9
10

1a. What proportion of your population has a dominant genotype? A recessive genotype?

1b. What are the phenotypic proportions of your population? (e.g., percentage of individuals with brown eyes?)

2. The allele for a widow’s peak hairline is dominant (W, dips down in the front), whereas a non-widow’s peak hairline is recessive (w, runs horizontally straight).

Widow’s peak Non-Widow’s peak

2a. Pick an imaginary partner (they can be anyone you know, celebrity, etc.). What is your partner’s phenotype? ________________________________________________

2b. What are the possible genotypes of your partner? ____________________________

2c. If you and your partner mated, what would your potential offspring look like in terms of having a widow’s peak? Solve this problem through Punnett squares (you may need to complete more than one).

3. The allele for attached earlobes is recessive (e) (fully attached to the side of the head), whereas unattached earlobes is dominant (E) (free hanging away from the side of the head).

3a. Pick an imaginary partner (they can be anyone you know, celebrity, etc.). What is your partner’s phenotype? ________________________________________________

3b. What are the possible genotypes of your partner? ____________________________

3c. What were the genotypes of your partner’s parents? Solve this problem through Punnett squares (keep in mind that there may be more than one possibility and you may need more than one square).

4. The curly hair allele is dominant (HH), straight hair is recessive (hh), and wavy hair is heterozygotic (Hh) (this is an example of incomplete dominance). Two wavy haired parents have a child.

4a. Complete the Punnett square for this cross in the space below.

4b. What is the probability that their first child will have wavy hair? _________________

4c. What is the probability that their second child will have wavy hair? ______________

4d. The couple is thinking about having a third child. What is the probability that the third child will have straight hair?