Define linked genes.

In cats, the allele for curled ears (C) is dominant over the allele for normal ears (c). The allele for black colour (B) is dominant over the allele for grey colour (b).  A cross occurs between two cats that are both heterozygous for these unlinked traits.

Using a Punnett grid, predict the ratio of phenotypes of offspring in the next generation.

Genes located on the same chromosomes.

a. Punnett grid correctly drawn / correct gametes;
b. phenotype ratio 9:3:3:1;
c. correct identification of expected phenotypes (9) black cats with curled ears, (3) grey cats with curled ears, (3) black cats with normal ears, (1) gray cat with normal ears;

A surprising number failed to define this term correctly.

Most candidates earned at least some marks on this question. A number of candidates could not correctly identify gametes. Some made errors in counting the numbers of different phenotypes in the grid leading to incorrect ratios. Only a few candidates failed to identify the phenotypes.