Question

A heterozygous tall plant of pea is crossed with a dwarf plant of pea. Calculate the phenotypic ratio of the progeny.

Answer 1

Hint: Mendel experimented with the inheritable traits of the pea plant and gave various theories related to the inheritance. He chooses the pea plant and its seven physically present characters to study. The control in the pollination is easy in pea plants making it suitable for the experiment.

Complete answer:
The cross made between the parent plants can be studied using the punnett square. It gives an idea of what type of progeny can be expected in the results.

T	t
Tt	tt	t
Tt	tt	t

When a heterozygous tall plant is crossed with the dwarf plant, a monohybrid cross is used as the only single trait of the plant which is height. In this situation, the dominant trait of the allele is assigned with the ‘T’ and the recessive allele is denoted as the ‘t’. Here tallness of a plant is considered to be dominant and the dwarfness of the plant is said to be recessive. So, if a plant is tall it would contain ‘TT’ which is pure tall and in the heterozygous condition it would contain ‘Tt’. And the dwarf planet would always have ‘tt’. So, when a heterozygous tall plant is crossed with the dwarf plant then the progeny obtained would be in the ratio 1:1 where half of them would be tall and the other half would be dwarf.

Note:
The punnett square is used in different types of crosses which are monohybrid cross where the only character is taken into the study, dihybrid cross where two characters are studied together, and the trihybrid cross in which three characters are studied together.