Question

In pea plants, the allele for tallness (T) is dominant over the allele for shortness (t). If two tall pea plants are crossed, can you predict the height of the offspring? Use logical reasoning to support your answer.

Answer 1

It is possible to predict the probabilities of the offspring however there are actually 4 different scenarios with 2 possible outcomes. Since the tall allele is dominant and we are breeding 2 tall plants, a tall plant could have be homozygous dominant (TT) or heterozygous (Tt) but still express the Tall phenotype. So the three different scenarios would be: 1) Both parents are homozygous dominant 2) Female is heterozygous and Male is homozygous dominant 3) Female is homozygous dominant and Male is heterozygous 4) Both parents are heterozygous. The two outcomes would be if the parents are in case 1, 2, or 3 all the offspring would be tall because at least one parent would only have the possibility of producing a Tall gamete which would cause the offspring to express the tall phenotype no matter what the other gamete is. Now if the parents were those in case 4 there is a 75% chance the offspring would be tall and a 25% chance the offspring would be short which can be proven by a punnett square.