Question

Four-o’ clock flowers may be red, pink or white. In the crossing of true-breeding red and true-breeding white plants, all the offspring are pink. Use a Punnett square to determine the correct genotype of the offspring if the red parent has genotype RR and the white parent has genotype rr.

(A) RR and Rr
(B) Rr and rr
(C) Rr only
(D) RR only

Answer 1

C) Rr Only

Step-by-step explanation:

The genotype of true breeding red parent plant is "RR" and that of the true breeding white parent plant is "rr". The red parent plant with "RR" genotype will form all the gametes with "R" allele while the white parent plant with "rr" genotype will form all the gametes with "r" allele. The random fusion of these gametes will form all the progeny with "Rr" genotype.

Since "R" is incompletely dominant over "r", the progeny with "Rr" genotype would have pink flowers.