Two genes

When two genes are involved, there are two possibilities:

• The genes lie on different chromosomes. (this part)
• Linkage: the genes lie on the same chromosome, the two genes belong to the same linkage group. (see the part about recombination)

I'll start with the easy case: the genes reside on a different chromosome.

When the gametes are formed at meiosis the different chromosomes divide independently of each other. Hence the first gene pair is not linked to the second and there will be no prefered combinations of an allele from the first and the second gene.

The way to go about it in practice is

When two genes located on different chromosomes are involved: Find the gametes for each gene seperatly as if this gene is the only one involved. Make all the possible combinations, one allele for each gene, to become the gametes. Note: Each gamete is equally likely to occure.

See it in practice with Example 3.