Question

If an allele for tall (T) is dominant to an allele for short (t), what proportion of the progeny will be tall in the following cross: Tt x TT?

Answer 1

In the genetic cross Tt x TT, where 'T' represents the dominant allele for tallness, 100% of the progeny will be tall, as they will all inherit at least one 'T' allele, which is sufficient for the tall phenotype to be expressed.

Step-by-step explanation:

When considering the cross Tt x TT, where 'T' is the dominant allele for tallness and 't' is the recessive allele for shortness, we can predict the phenotypic outcome. A Punnett square would show that all offspring could inherit a 'T' allele from the TT parent and either a 'T' or a 't' allele from the Tt parent. This results in possible genotypes of TT and Tt. Since the presence of at least one 'T' allele results in a tall phenotype, 100% of the progeny will be tall.

The Punnett square for this cross would look like this:

• TT (from Tt parent) x TT (from TT parent) = TT
• Tt (from Tt parent) x TT (from TT parent) = Tt

Thus, whether the offspring are homozygous dominant (TT) or heterozygous (Tt), they will all exhibit the tall phenotype as the tall trait is dominant. There will be no short progeny in this cross.