Question

If we cross pure-bred tall (dominant) pea plant with pure-bred dwarf (recessive) pea plant we will get pea plant of $F1$ generation, then we obtain pea plants of $F2$ generation.
(a) What do the plants of $F1$ generation look like?
(b) State the ratio of tall plants to dwarf plants in $F2$ generation.
(c) State the type of plants not found in $F1$ generation but appeared in $F2$ generation, mentioning the reason for the same.

Answer 1

When there is a cross between pure-bred tall pea plants with pure-bred dwarf pea plant the $F1$ generation formed has a genotype of TT. When the $F2$ generation is further cross-bred it results in the formation of tall plants of major ratio and dwarf plant of minor ratio.

Complete step by step answer: a).. In the monohybrid cross between tall and dwarf plants, only tall plants appear in the $F1$ generation. This happens due to the reason that for a trait of plant height there occurs two types of allele, T for tall and t for dwarf (T is dominant over t). When a purebred tall plant (TT) is crossed with pure-bred (TT) it results in a heterozygous tall plant (Tt), this due to the masking of expression of the recessive allele t by the dominant allele T.
b). When the $F1$ generation (Tt) is allowed to be self-fertilized, both tall and dwarf characters appear in the $F2$ generation. The phenotypic ratio of tall plants to dwarf plants is $3:1$

| T| t
---|---|---
T| TT| Tt
t| Tt| tt

c). Dwarf plants are not found in $F1$ generation but appeared in the $F2$ generation. In the $F1$ generation hybrid, the character of tallness dominates the character of dearness due to which it is unable to express itself in $F1$ generation.

Note: In a monohybrid cross between a tall and a dwarf plant the $F1$ generation produced is all tall. When these $F1$ offspring are self-crossed it results in the formation of both tall and dwarf plants in the ratio of $3:1$. Dwarf plants are not found in the $F1$ generation due to the masking of expression of a recessive allele by the dominant allele.