Question

In four o'clock plants, the gene for red flower colour (R) is incompletely dominant over the gene for white flower colour (r), hence the plants heterozygous for flower colour (Rr) have pink flowers. What will be the ratio of offsprings in a cross between red flowers and pink flowers?

• A. 75% red flowers, 25% pink flowers
• B. All red flowers
• C. 50% red flowers, 50% pink flowers
• D. Red : pink : white- $1:2:1$

Answer 1

Answer: (C)

Incomplete dominance is a deviation of Mendel's law of dominance where the heterozygous individual instead of expressing the dominant trait, it expresses a trait which is a mix of the parent traits.
On crossing red homozygous flowers of four o'clock plant with pink flowers of four o'clock plant, the following genotypes and phenotypes are obtained:

Parent	Red (RR) X	Pink (Rr)
Gametes	R	R,r
$F_1$ generation	RR	Rr

Phenotypes: Red (50%) and Pink (50%)
Genotypes: RR (50%) and Rr (50%)