Question

Which of the following crosses will give recessive progeny in F1 progeny?
A. TT × tt
B. Tt × TT
C. tt × tt
D. TT × TT

Answer 1

We must know that recessive progeny means when both the alleles for a particular trait are recessive. Recessive alleles mean those alleles which are not able to express themselves in the presence of dominant alleles. Here tt will represent the recessive progeny.

Complete answer:
To know the correct answer of the question, we must be well aware of the crosses. We must know how to make the crosses. In the given question, we have taken height as the trait. In this cross TT stands for homozygous tall and Tt stands for heterozygous tall while tt stands for homozygous dwarf.
The homozygous genes are those which have the same allele on both the homologous chromosomes while heterozygous genes are those which have different alleles on both the homologous chromosomes.
The dominant allele of a trait always suppresses the expression of the recessive one. The alleles segregate and then come together. For example: Here both the parents are homozygous dwarf so after the cross, the progeny that we will get will be homozygous dwarf.

| t| t
---|---|---
t| tt| tt
t| tt| tt

Therefore, the correct answer to the question is tt × tt.

Note: Here, it must be noted that to get the recessive allele, atleast one of the alleles in both the genes must be recessive. These genes will segregate and when the cross will be formed then atleast one of the progeny will be recessive.