The traits in the organisms are controlled by the genes which are present in the form of two alleles on the chromosomes. Each allele represents the variant of the trait which is determined when these alleles unite during sexual reproduction.
The allele can be dominant when it shows its effect or it can be recessive when it is suppressed during fusion.
In the given question, the studied trait is the pattern of the hair which is present in two variants: the curly hair and the straight hair. When the parents for these traits were crossed they produced offspring which was intermediate between the curly and the white hair. This intermediate trait shows that neither of the two alleles which control the trait is dominant and the trait blended. This natural process is known as incomplete dominance.
