Question

In peas, a gene for tall plants (T) is dominant over its allele for short plants (t). The gene for smooth peas (S) is dominant over its allele for wrinkled peas (s). The genes are not linked. Determine both phenotypic and genotypic ratios for the results of each of the following crosses:

1.1 homozygous tall wrinkled x short heterozygous smooth.                  [26 marks]

1.2. short heterozygous smooth x heterozygous tall wrinkled.                 [26 marks]

1.3 heterozygous tall homozygous smooth x short wrinkled.                  [26 marks]

Answer 1

The phenotypic ratios are the ratios of visible characteristics. The genotypic ratios are the ratios of gene combinations in the offspring, and these are not always distinguishable in the phenotypes.