punnett squares
Punnett squares are very useful when trying to determine the possible genotypes and phenotypes of an offspring based on the parents genetic information.
In the image to the left, we are crossing two pea pods. Y is the dominant allele for a yellow pea pod and y is the recessive allele for a green pea pod. We're crossing a yy pea pod with a Yy pea pod.
To use a punnet square, you first need a box with four sections. Then you put the genotype of one parent across the top and that of the other parent down the left side. Remember that only one letter goes on each side for the parents. It does not matter which parent is on the side or the top. Next, all you have to do is fill in the boxes by copying the row and column-head letters across or down into the empty squares.
Each box represents the possible genotype of the offspring.
In the case of the punnett square to the left, there is a 50-50 chance the pea pod will be yellow.
image source : http://en.wikipedia.org
To use a punnet square, you first need a box with four sections. Then you put the genotype of one parent across the top and that of the other parent down the left side. Remember that only one letter goes on each side for the parents. It does not matter which parent is on the side or the top. Next, all you have to do is fill in the boxes by copying the row and column-head letters across or down into the empty squares.
Each box represents the possible genotype of the offspring.
In the case of the punnett square to the left, there is a 50-50 chance the pea pod will be yellow.
image source : http://en.wikipedia.org