# How do you do probabilities with punnett squares?

##### 1 Answer

Nov 9, 2016

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 |

*_*_|

*|***|**

*_*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 %