Question

In snapdragons, flower color is controlled by incomplete dominance. The two alleles are red (R) and white (W). The heterozygous phenotype is pink. If a white and a red plant are crossed, what is the probability of getting a white plant?

a) 0%
b) 25%
c) 50%
d) 75%

Answer 1

The probability of getting a white snapdragon plant from a cross between a pure red (RR) and a pure white (WW) snapdragon is 0% because all offspring will be pink (RW) in the case of incomplete dominance.

Step-by-step explanation:

In snapdragons, flower color exhibits incomplete dominance, where the heterozygote shows a phenotype that is intermediate between the two homozygous parents. When a homozygous white flower snapdragon (genotype WW) is crossed with a homozygous red flower snapdragon (genotype RR), all the F1 offspring will be heterozygous with a pink flower phenotype (genotype RW). If the question is asking about the probability of getting a white plant from this specific cross (RR x WW), the answer is 0% since all offspring will be heterozygous and display pink flowers.

The genotypic ratio for a cross between two pink snapdragons (RW x RW) however, is 1 red: 2 pink: 1 white (genotypic ratio 1:2:1). In this scenario, the probability of getting a white plant would be 25%.