A) What Are the Possible Genotypes for a Person with Albinism?

Year 10 science 1 Genetics – Worksheet 1

1. Albinism is a hereditary condition in which skin pigments are not formed. Normal skin pigmentation (P) is dominant over albinism (p). a) What are the possible genotypes for a person with albinism? b) What are the possible genotypes for a couple with albinism? c) If the first child of a married couple with normal phenotypes is an albino, what are the chances that their second child will also be an albino? Explain your answer.

2. The gene for a long nose (N) is dominant over the gene for a short nose (n). a) What possible genotypes can a long-nosed person have? b) What possible genotypes can a short-nosed person have? c) If a pure long-nosed person marries a person who has a short nose, what types of noses can their children have? Show reasons.

3. In cats, short hair (H) is dominant over long hair (h). Two cats heterozygous for hair length are crossed. Use a punnet square to help answer these questions. a) What is the genotype of the heterozygous cat? b) What are the possible genotypes of the offspring? c) What are the possible phenotypes of the offspring? d) What percentage of offspring would be expected to have each of the phenotypes listed in c?

4. In pigs the gene which produces a white belt around the animal (W) is dominant over the gene for uniform colour(w). A pig heterozygous for colour is crossed with a pig homozygous for uniform colour. Use a punnet square to help answer these questions. a) What are the possible genotypes of the offspring? b) What percentage of offspring would be expected to have each of the genotypes listed in a? c) What percentage of offspring would be expected to have uniform colour?

5. The eye colour of a fruit fly is determined by a single gene which has dominant and recessive alleles. The allele for red eyes (R) is dominant over the allele for white eyes (r). P1 R r P2 r Rr rr r Rr rr

a) What colour eyes does parent 1 have? b) What colour eyes does parent 2 have? c) Which parent is homozygous for eye colour? d) What percentage of offspring would be expected to have white eyes? e) What percentage of offspring would be expected to be heterozygous for eye colour?