Question

What is Mendel's third law?

Answer 1

Mendel's third law:

1. Mendel's third law of inheritance is the law of independent assortment.
2. According to this law, discrete pairs of alleles pass onto the children without being dependent on one another and as a result, the inheritance of genes in a particular region of the genome has no effect on the inheritance of genes in another region.
3. Mendel's experiments consistently showed that the combination of traits in the progeny is always distinct from their parents and on this basis, the law of independent assortment was postulated.

Reasons for independent assortment:

1. During the meiosis, independent assortment occurs and the chromosome number is reduced to half which results in the formation of haploid gametes.
2. The law of independent assortment applies when the maternal and paternal genes are randomly partitioned.

Mendel's experiments to prove the law of independent assortment:

1. The law asserts that an assortment of each pair of traits is independent of the other during a dihybrid cross.
2. This allows each pair of traits to express themselves.
3. In a dihybrid experiment, Mendel selected two traits, each with two alleles.
4. He crossed round-yellow seeds (dominant) and wrinkled-green seeds (recessive) and observed that all of the F₁ progeny were round-yellow.
5. He then self-pollinated the F₁ progeny and obtained four distinct phenotypes that are round-yellow, round-green, wrinkled-yellow, and wrinkled-green seeds in the phenotypic ratio of 9:3:3:1.