Question

Results of two or three factors crosses can be easily analysed by
A) Principle of segregation
B) Principle of dominance
C) Principle of independent assortment
D) Both A and B

Answer 1

Factor means gene or allele. Every character of an individual is controlled by Factor(gene) and factors always occur in pairs. The third law of inheritance is the principle of independent assortment, which was proposed by Mendel , based on the results from dihybrid cross, which involves two or more factors.

Complete answer:
There are three laws of inheritance proposed by Mendel-
Law of dominance- It was based on monohybrid cross (cross between two parents which involves only a single character, hence one trait/ gene is involved). It states that, in a dissimilar pair of factors , one member (allele) of the pair will dominate over the other.
Law of segregation - This law was also the result of monohybrid cross. It states that , at the time of gamete formation , a pair of factors (allelic pair) is separated from each other and they get united at the time of fertilisation.
Law of independent assortment - The law was proposed based on the results from dihybrid cross. This law states that the assortment of alleles of one pair is independent of the assortment of alleles of another pair at the time of gamete formation. Therefore , two or more factors can be involved in independent assortment.

Let us analyze the options to find the correct answer:
Option A : The principle of segregation was based on the result from monohybrid cross. It states that the two factors of single trait separated at the time of gamete formation and reunited at the time of fertilisation. Hence, this is an incorrect option.

Option B: The principle of dominance is based on the one factor of a trait. In a heterozygous pair of factors , one member of the pair will dominate over the other. Hence, this is an incorrect option.

Option C: THe principle of independent assortment was based on the dihybrid cross (involves two traits). During meiosis ,independent assortment in non- homologous chromosomes results in an independent assortment of alleles of one pair to the allele of another pair. Hence, this is the correct option.

Option D: As both the option A and B is incorrect, Hence, this is an incorrect option.

Thus , the correct answer is option (C) Principle of independent assortment.

Note:
i) Mendel’s rules are only applicable to diploid sexually reproducing individuals.
ii) Nowadays , factors are known as gene / allele.
iii) If the two alleles that form the pair for a trait are identical, then the individual is said to be homozygous and if the two genes are different, then the individual is heterozygous for the trait.