Answer to Question #245503 in Genetics for Tumzaza

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:

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

Answer 1

In most of the cases Dominant allele expresses their character even if present in heterozygous form but recessive characters needs 2 alleles(homozygous)to be expressed. 

Exception is, in epistasis may be the dominant character not express due to other allele effect. 

The ratio is 1:1 in both phenotype and genotype case. 

The cross is explained below.

Here P =Given parents 

G= Gametes produced by them.