Genetics worksheet with answers

In pea plants, purple flowers (A) are dominant over white (a). A plant with genotype Aa is crossed with a plant with genotype aa. What is the probability P that an offspring is heterozygous (Aa)?

Two Tt parents are crossed. T gives black fur and is dominant over t, which gives white fur. Click the cell of the Punnett square for an offspring with white fur.

1. 1t × t
2. 2t × T
3. 3T × t
4. 4T × T

red-green colour blindness is X-linked recessive (allele b). A carrier mother, X^BX^b, has children with an affected father, X^bY. The mother's gametes run down the side. Click the cell for an unaffected son.

1. 1X^b × X^b
2. 2X^b × Y
3. 3X^B × X^b
4. 4X^B × Y

Tall (A) is dominant over short (a), and round seeds (B) over wrinkled (b). The genes are on different chromosomes. For the cross AaBb × Aabb, what is the probability P that an offspring is short, round seeds?

Two AaBb parents are crossed. Gene A gives round seeds (dominant) or wrinkled seeds; gene B gives yellow seeds (dominant) or green seeds. Click the one cell for an offspring that is shows wrinkled seeds and is homozygous for yellow seeds.

1. 1aB × ab
2. 2aB × aB
3. 3aB × AB
4. 4aB × Ab
5. 5ab × ab
6. 6ab × aB
7. 7ab × AB
8. 8ab × Ab
9. 9Ab × ab
10. 10Ab × aB
11. 11Ab × AB
12. 12Ab × Ab
13. 13AB × ab
14. 14AB × aB
15. 15AB × AB
16. 16AB × Ab

A recessive condition affects 1 in 2500 of a population in Hardy–Weinberg equilibrium. What fraction f of the population are carriers (heterozygous)?