What is Mendel's law of independent assortment?
Mendel's Law of Independent assortment is a law stating that allele pairs separate independently during gametes formation.
- The law is only true for traits that are not linked ( seed color vs. seed shape).
- When two or more characteristics are inherited by an individual, those characteristics assort independently during gamete production.
- This gives the various traits an equal opportunity of occurring together.
- In other words: the inheritance of one trait will not affect the inheritance of another.
Law of Independent Assortment example:
Mendel's Law of Independent Assortment states that the segregation of the factors or Genes representing two traits is independent of each other.
Mendel's Law of Independent Assortment explains the inheritance
of two traits of a plant together. This can be explained by taking the example of inheritance of height and color of flower together in pea plant. This type of cross is termed dihybrid cross.
A pure tall plant bearing red flowers is crossed with pure dwarf plant bearing white flowers. The plants produced as a result of this cross are all tall plants bearing red flowers, constituting Ist filial generation or F1 generation.
Plants of F1 generation are allowed to interbreed freely among themselves to get F2 generation. The plants of F2 generation have 4 different phenotypes, i.e. tall red, tall white, dwarf red and dwarf white in the ratio of 9:3:3:1. This is termed dihybrid phenotypic ratio.
These results obtained in dihybrid cross could be explained by assuming that segregation of the genes of two traits, i.e height and the color of the flower occurs independently of each other. In other words, the segregation of the genes of one trait does not affect the segregation of the genes of other trait.
A homozygous tall and homozygous red plant (TRTR) is crossed to homozygous dwarf and homozygous white plant (trtr). The plant of F1 are heterozygous tall and heterozygous red (TRtr).
On crossing plants of F1, the gametes produced by two plants will have 4 genotypes, if we assume that the segregation of genes of two traits is independent of each other. 4 types of gametes formed will have genotype TR, Tr, tR and tr.
Each of the 4 types of gametes formed by one plant has equal chances of fusing with each of the 4 types of the gametes formed by the other plant. The possible permutation and combination of these gametes will produce tall red, tall white, dwarf red and dwarf white plants in the ratio of 9:3:3:1, as is actually observed.
Mendel observed that the actual results observed in dihybrid cross were the same as calculated results on the basis of assumption that the segregation of genes of 2 traits is independent of each other. He thus proposed the Law of Independent Assortment, which states that the segregation of genes of 2 traits is independent of each other.