Question

In a cross between a homozygous tall pea plant with green pod (TTGG) and a homozygous short plant with yellow pod (ttgg), how many short plants out of 16 you would expect in F${}_2$ generation?

• A. 3
• B. 4
• C. 9
• D. 1

Answer 1

Answer: (B)

4

The genotype of homozygous tall plants with green pods: TTGG

Therefore, gametes will be - TG
The genotype of homozygous short plants with yellow pods: ttgg

Therefore, gametes will be - tg
F${}_1$ Generation: TtGg
Selfing of F${}_1$:

Gametes	TG	Tg	tG	tg
TG	TTGG	TTGg	TtGG	TtGg
Tg	TTGg	TTgg	TtGg	Ttgg
tG	TtGG	TtGg	ttGG	ttGg
tg	TtGg	Ttgg	ttGg	ttgg

Tall is the dominant trait, whereas short is recessive.

Thus, the short trait will get expressed only when it is homozygous. The genotypes with homozygous short alleles (tt) are: ttGG, ttGg and ttgg

Out of 16 plants produced in the F${}_2$ generation, 4 plants possess the above-mentioned genotypes and are thus expected to be short in height.