Question

tall heterozygous pea plants were crossed and the resulting seeds grown. Out of 360 plants, 270 were tall and 90 dwarf. What describes the expected genotype resulting from the cross

Answer 1

Answer:

This question lacks options, the options are:

A. All 270 tall plants were heterozygous

B. All 270 tall plants were homzygous.

C. Only 90 plants were homzygous.

D. All dwarf plants were homzygous.

The answer is D.

Explanation:

This question involves a single gene coding for height in pea plants. The allele for tallness (T) is dominant over that of dwarfness (t). This means that a dwarf plant can only be homzygous recessive (tt) while a tall plant can either be homzygous (TT) or heterozygous (Tt).

According to the question, two tall heterozygous pea plants were crossed i.e. Tt × Tt. Based on this cross, a phenotypic ratio of 3:1 is expected, which is in accordance with the 270 tall plants and 90 dwarf plants (360 total) that was obtained in the cross. Since dwarfism in pea plants is a recessive trait, this means that all the dwarf plants produced in this cross (90) were homzygous (tt).