This diagram is called a punnet square and as a way to represent the possible combinations of chromosomes in sexual/sex inheritance. The pairs of letters in each of the 4 square boxes shows the possible combination of X and Y chromosomes along the edges. You should be able to see that in this particular combination there are 2 XX combination possibilities and 2 XY combination possibilities.


This tells us that the probability of the offspring being male is 50% and the probability of the offspring being female is also 50%. You should remember though that this is only a mathematical probability, not a guarantee at the in fact in a multiple pregnancy all of the offspring could be the same-sex.


If you fancy a trip down "Mathematics Street" you can click here for a review on the topic of "probability". Don't forget to come back though.



There is an alternative type of diagram, which provides the same information as a punnet square but it is a little bit more complicated to get your head round.



>> Questions <<