How do you do probabilities with punnett squares?

Nov 9, 2016

Answer:

The number of squares with the outcome divided by the total number of squares. This can be expressed as a fraction or percentage.

Explanation:

A Classic example is the bi hybrid cross of both parents being brown /blonde

$$ Mother          B         b      Father


__|__||
B | B B | B b |
_
|__||_
b | b B | b b |
_|__||___

There is one off spring square bb that will give rise to a blonde
off spring There are four total squares.

So the probability is 1/4 of having a blonde child This translates to a 25% probability of having a blonde.

There are three square that will result in a brown haired offspring.

so the probability of a a brown haired off spring is 3 out of 4 or

3/4 or 75 %