22. In a flower species, light pink locus is hypostatic to pigment development locus. R is for pigment development and W for light pink. The recessive allele (w) in light pink locus gives red colour and recessive allele in pigment locus (r) gives white colour.
What will be the phenotype of W/-, r/r and w/w, r/r?
(1) Red, Pink       (2) Pink, White
(3) Red, Red       (4) White, White

Explanation

Genetic basis

• R locus controls pigment development:

  • R (dominant) = pigment produced

  • r (recessive) = pigment absent → white

• W locus controls the shade:

  • W (dominant) = light pink

  • w (recessive) = allows red if pigment is present

• W is hypostatic (its effect depends on pigment being present; cannot show in absence of pigment).

Phenotype breakdown

1. W/-, r/r (Pink):

   • W present, but pigment locus is r/r

   • r/r means no pigment is made, so the flower cannot be red.

   • W expresses as pink, but in the absence of pigment, this locus leads to pink phenotype.

2. w/w, r/r (White):

   • Only recessives present, r/r means no pigment.

   • w/w removes the pink factor, but no pigment is present (r/r), so flower shows as white.

Option-by-option analysis

1. Red, Pink – Incorrect.

   • Both r/r genotypes lack pigment; red only appears with w/w but with pigment (R/_).

2. Pink, White – Correct.

   • W/-, r/r = pink.

   • w/w, r/r = white.

3. Red, Red – Incorrect.

   • r/r locus always gives no pigment, so red is not possible.

4. White, White – Incorrect.

   • Only w/w, r/r is true white; the other genotype is pink.

Thus, in summary: W/-, r/r = pink; w/w, r/r = white.