Question

The gene combination of purple flowered pea plants is denoted as (WW) and that of white flowered pea plants as (ww), when these two plants are crossed F₁ generation is obtained.

1. List two observations made by Mendel in F₁ generation plants.
2. Give the (i) percentage of white flowered plants and (ii) ratio of the gene combinations WW, Ww and ww in F₂ generation.
3. Write one difference between dominant and recessive trait.

Answer 1

a. Two observations made by Mendel in F₁ generation plants:

1. The fact that all F₁ plants had purple flowers (Ww) indicates that purple is more common than white.
2. The F₁ generation did not exhibit the white flower feature (ww), whereas the F₂ generation did.

b. WW - Purple flower, ww - white flower

F₁ generation:

	W	w
W	WW	Ww
W	WW	Ww

F₂ generation:

	W	w
W	WW	Ww
W	WW	Ww

(i) WW: Purple homozygous flowers (25%)

Ww: Purple heterozygous flowers (50%)

ww: White homozygous flower (25%)

(ii) Using a Punnett square, the expected genotype ratio is:

WW : Ww : ww = 1 : 2 : 1

c. Recessive traits are those that only manifest in homozygous (ww) conditions and remain hidden in heterozygous forms, whereas dominant traits are present in both homozygous (WW) and heterozygous (Ww) forms.