(a) This is an exception to Mendel’s principle of dominance and can be explained by the phenomenon of ‘Incomplete dominance’. It is a phenomenon where none of the two contrasting alleles or factors are dominant. The expression of the character in a hybrid or F1 individual is intermediate or a fine mixture of expression of the two factors (pink flowers in this case from two parents with red and white flowers). This may be considered as an example of quantitative inheritance where only a single gene pair is involved. F2 phenotypic ratio is 1 : 2 : 1, similar to the genotypic ratio, in which the parental characters also reappear. 

(b) Mendel’s Laws of Inheritance 

▪ Based on his hybridisation experiments, Mendel proposed the laws of inheritance. 

▪ His theory was rediscovered by Hugo de Vries of Holland, Carl Correns of Germany and Eric von Tschermak of Austria in 1901. 

(i) Law of dominance 

▪ This law states that when two alternative forms of a trait or character (genes or alleles) are present in an organism, only one factor expresses itself in F1 progeny and is called dominant while the other that remains masked is called recessive. 

(ii) Law of segregation. 

▪ This law states that the factors or alleles of a pair segregate from each other during gamete formation, such that a gamete receives only one of the two factors. They do not show any blending.