Sample Problem

Pea plants can have two alleles for height: T (tall stem) and t (short stem). Two plants with genotype Tt and tt are crossed, and the 300 resulting seeds are planted. How many of the offspring are predicted to be short? Write your answer as a whole number with no decimals.


Draw a Punnett square and fill it in. It should look something like this:

Only the tt genotype would code for short pea plants. That means it is predicted that ½ of the offspring will be short.

½ x 300 = 150

So 150 of the offspring are predicted to have short stems.