How do I work out a genetic cross?
- Note the phenotypes of the parents, work out whether they are homozygous or heterozygous.
- Choose letters to represent the alleles. The upper case letter should represent the dominant alleles and the lower case represents the recessive ones.
- The parents should be labelled and their phenotypes represented with a pair of letters.
- State the gametes each parent would produce. Label them.
- Use a Punnet square to show how the gametes would cross.
- State the phenotype of each genotype and indicate the ratio.
