What do the letters outside the punnett square stand for?
The letters on the outside of a Punnett square stand for the parent alleles. The alleles are represented by upper case letters and lower case letters, depending on the dominance or recessiveness of a trait. Punnett squares can be as simple as four boxes or as complex as thirty-six boxes. When filling in a Punnett square one should place the parent the two parents at the top and the left side and place the seperated alleles on the top and sides corresponding to the rows and columns of the square.
