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 Rr parents are crossed. R gives black fur and is dominant over r, which gives white fur. Click the cell for an offspring that has black fur and is homozygous.

1. 1R × r
2. 2R × R
3. 3r × r
4. 4r × R

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 affected daughter.

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

haemophilia is X-linked recessive (allele h). A carrier mother, X^HX^h, has children with an affected father, X^hY. The mother's gametes run down the side. Click the cell for an affected son.

1. 1X^h × X^h
2. 2X^h × Y
3. 3X^H × X^h
4. 4X^H × Y

Two AaBb parents are crossed. Gene A gives black fur (dominant) or white fur; gene B gives purple flowers (dominant) or white flowers. Click the one cell for an offspring that is homozygous for black fur and shows white flowers.

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 400 of a population in Hardy–Weinberg equilibrium. What fraction f of the population are carriers (heterozygous)?