Question

A homozygous tall plant (T) bearing smooth pod(S) is crossed with a dwarf plant(t) bearing wrinkled pod (s).
i. Write the genotype and phenotype of $F_1$
v. State Mendel's Law of dominance.

Answer 1

Gametes	TS	Ts	tS	ts
TS	TTSS- Homozygous Tall and Homozygous smooth pod	TTSs- Homozygous Tall and Heterozygous smooth pod	TtSS- Heterozygous Tall and Homozygous smooth pod	TtSs- Heterozygous Tall and Heterozygous smooth pod
Ts	TTSs-Homozygous Tall and Heterozygous smooth pod	TTss-Homozygous Tall and Homozygous wrinkled pod	TtSs-Heterozygous Tall and Heterozygous smooth pod	Ttss- Heterozygous Tall and homozygous wrinkled pod
tS	TtSS- Heterozygous tall and Homozygous smooth pod	TtSs-Heterozygous Tall and Heterozygous smooth pod	ttSS- Homozygous dwarf and homozygous smooth pod	ttSs- homozygous dwarf and Heterozygous smooth pod
ts	TtSs-Heterozygous Tall and Heterozygous smooth pod	Ttss- Heterozygous tall and homozygous wrinkled pod	ttSs- homozygous dwarf and Heterozygous Smooth pod	ttss- homozygous dwarf and homozygous wrinkled pod.

i. cross for F1 generation formation ( TTSS x ttss)

TS x ts $\to$ TtSs, All the progenies will be of this genotype. The phenotype will be Heterozygous Tall and Heterozygous smooth pod.

ii. A number of gametes = 2${}^n$, where n is a number of the heterozygous allele.

So, from TtSs number and types of gametes possible are 2${}^2$= 4 i.e.,

TS

Ts

tS

ts

iii.Punnet square for F2 generation: cross between TtSs x TtSs

iv. The phenotypic ratio of F2 generation is 9:3:3:1:: Tall and smooth pod: Tall and wrinkled pod: dwarf and smooth pod: dwarf and wrinkled pod

v. Mendel's Law of dominance: In heterozygous genotype, one allele expresses itself phenotypically and other allele remains suppressed. Law of dominance can be explained with F1 results of a monohybrid cross.