Question

What would be the colour of flower in F1​ progeny as a result of cross between homozygous red and homozygous white flowered Snapdragon?
A. Red
B. White
C. Red and white
D. Pink

Answer 1

Hint: In Mendel's work on pea plants, each gene came in just two different versions or alleles, and these alleles had a clear-cut dominance relationship that the dominant allele overrides the recessive allele for plant determination.

Complete answer:
Mendel’s results were groundbreaking partly because they contradicted the idea that the parents' traits were permanently blended in their offspring. In some cases, however, the phenotype of a heterozygous organism can actually be a blend between the phenotypes of its homozygous parents.
For example, in the snapdragon, a cross between a homozygous white-flower (rr) and homozygous red flower(RR) is made a pink flower formed this is the case of incomplete dominance.
Snapdragon plant shows incomplete dominance of flower colour. It means that one allele for the flower colour is not completely dominant over the other one and thus the heterozygous genotype shows a combination of dominant and recessive phenotypes. If the red colour was completely dominant over white colour then the F1​ hybrid would show red flowers If the red and white colour were codominant, none of them was dominant, the F1​ hybrid would show red and white flowers; White colour is recessive which is not expressed in a hybrid; option B is wrong.

Hence the correct answer is OPTION(D)

Note: In codominance, both alleles are completely expressed. If we crossed a red flower with a white one and the alleles were codominant, we get flowers that are red and white in patches. If the alleles were incompletely dominant, the flowers would be pink because the traits blend.