Square used to explain
genetic traits. The
sperm's
genotype is listed on the left and the
egg's on the top, then the traits are
crossbred. For example, the sperm genotype that determines the sex of a baby is
XY and the egg genotype is
XX. This leads to this Punnett Square:
X X
X XX XX
Y XY XY
This means that there's a 50% chance that the baby will be a boy (XY) and a 50% chance that it will be a girl (XX).
The Punnett Square sometimes gets more complicated, but the idea remains the same. It works for all types of plants and animals, but some genes are a little too complicated to use a Punnett Square for.