Question

.What are the genotypes of the parents in the monohybrid cross below if the following offspring genotypes are predicted?

Answer 1

As you can see in the diagram presented below, the correct genotypes of the parents are TT and Tt.

Each parent give its children only one chromosome of the chromosome pair, therefore only one allele of the gene.

In our case, TT and Tt is the correct answer because one of the parents has to have the t allele to give to the Tt offspring.

But if both of the parents were Tt, one of the offspring would have tt genotype, and if the parents were TT and tt, all of the offspring would be Tt. Therefore, the TT x Tt combination is the only possible answer.

Answer 2

As we know that out of the two allelic pairs, each parent contributes only one allele at the time of gamete fusion, so these kind of progenies will be obtained only when both the parents are heterozygous for a particular trait.

Heterozygous parents for a particular trait produce off-springs with three types of genotypes mentioned as under :-

         Tt  x  Tt

                |

  TT    Tt      Tt      tt

It is clear from the above that basically 3 types of genotypes are obtained which are TT, Tt and tt.

If we will check the genotypes of all the off-springs in the question, they all will be included if a cross is made between parents with heterozygous genotype i.e. Tt x Tt.