Question

why multiple allelism is considered as extension of mendilism?

Answer 1

Mendel implied that only two alleles, one dominant and one recessive, could exist for a given gene. We now know that this is an oversimplification. Although individual humans (and all diploid organisms) can only have two alleles for a given gene, multiple alleles may exist at the population level, such that many combinations of two alleles are observed. Note that when many alleles exist for the same gene, the convention is to denote the most common phenotype or genotype in the natural population as the wild type (often abbreviated “+”). All other phenotypes or genotypes are considered variants (mutants) of this typical form, meaning they deviate from the wild type. The variant may be recessive or dominant to the wild-type allele.

Answer 2

Multiple alleles

Three or more alleles that can occupy a given gene locus are referred to as multiple alleles. The multiple alleles exist in a population. However, in a diploid individual only two alleles for a particular gene can exist as they are present on the homologous chromosomes. So, an individual would have two alleles for a single gene but different individuals will have different combinations of alleles for that gene. They always occupy the same locus and influence the same trait. Also, they are conspicuous only during population studies.


ABO blood group

The ABO blood group system in humans is the simplest example depicting multiple alleles. This system was discovered by Karl Landsteiner in the early 1900, who was awarded Nobel Prize in Physiology or Medicine in 1930 for this discovery. These alleles give rise to four possible phenotypes: A, B, AB, andi)represented here as )esttle isinvolved, chromosome 9 having three variant alleles gens on the surface of the red blood cells ( O blood groups.