Question

Dihybrid cross is related to
a. Principle of dominance
b. Principle of independent assortment
c. Principles of segregation
d. Principle of purity of gametes.

Answer 1

Hint: Dihybrid crosses are those crosses in which two pairs of contrasting characters are taken into account simultaneously. For example cross between pea varieties having green cotyledons and wrinkled seeds and yellow cotyledons and round seeds.

Complete answer:
> Principle of dominance
It states that when a pair of alleles or allelomorphs are brought together in F1 hybrid, then only one of them expresses itself, masking the expression of the other completely. For example, In Rr, the F1 hybrid is round as only ‘R’ expresses itself while ‘r’ is masked. So ‘R’ is dominant over ‘r’.

> Principle of independent assortment
It states that when two pairs of independent alleles are brought together in F1 hybrid, they show independent dominant effects i.e. in the formation of gametes law of segregation occurs and the factors assort themselves independently at random and freely.

> Principle of segregation or Principle of purity of gametes
According to this when a pair of allele or allele morphs are brought together in F1 hybrid, they remain together without mixing or contaminating or blending with each other and get separated during gametogenesis.

> The principle of dominance and principle of independent assortment were concluded by Mendel on the basis of his results of monohybrid crosses while the principle of segregation or principle of purity of gametes was based on the result of the dihybrid cross.

Hence, the correct answer is option (B).

Note: Mendel is called the “Father of Genetics”. He conducted hybridization experiments on 14 true breeding garden Pea for seven years and gave the basic principles of genetics. Monohybrid cross results in the Law of dominance and Law of segregation. Dihybrid cross results in the Law of Independent assortment.