Multiple Alleles or Polyallely
Multiple Alleles: The cases of multiple alleles, a phenomenon also called polyaelia, are frequent in both animals and plants.
The coat color of rabbits is a classic example of polyaelia.
When studying genetics we observe two qualities of allele genes. In albinism, A determines normal skin, and its a allele determines abnormal skin. In peas, R determines seeds with a smooth surface, while r determines seeds with a rough surface. As for the coat of guinea pigs, L determines ruffled hair, L determines smooth hair, and so on.
We know that genes are pieces of DNA, and that diploid organisms will always have two alleles of each gene, one from the father and one from the mother. Thus, certain genes can mutate over time, giving rise to multiple alleles. For example, if an A gene duplicates, it will give rise to two A genes identical to it. If these A genes also duplicate, they will also produce identical A genes. But if there is a mutation in this gene A , it will change and can then be called a . This modified gene will produce a different protein, perhaps because only one amino acid has been changed. The A gene and the a genethey can undergo one, two, three or several mutations, giving rise to a series of multiple alleles that control the same character. Thus, we can say that multiple alleles originate from mutations of preexisting genes . This phenomenon can also be called polyaelia.
To better understand polyaelia, we will cite the coat color of rabbits, which is a classic example of multiple alleles.
The C gene determines the coat color to be gray-brown ( wild or agouti ). The c ch gene determines the coat color to be silver gray ( chinchilla ). The c h gene determines white fur with dark ends ( Himalayan ), and finally the c gene , which determines white fur ( albin ). The C gene , which conditions wild fur, is dominant over the other three alleles, and the c ch gene , which conditions chinchilla fur, although it is recessive in terms ofgene C , is dominant over gene c h and gene c. The c h gene for the Himalayan is recessive to the C gene and c ch gene , but dominant over the c gene . The c gene , which conditions the albino phenotype, is recessive in relation to the three other types of genes.
|phenotype||Gene||dominance relationship||Possible genotypes|
|agouti or wild||Ç||dominates the other genes||CC or Cc ch or Cc h or Cc|
|Chinchilla||ch _||Himalayan and albino masters||c ch c ch or c ch c h or c ch c|
|Himalayan||c h||albino dominates||c h c h or c h c|
|Albino||Ç||Recessive towards others||cc|
Polyaelia is much more common than one might think. There are multiple alleles for the eye color of the banana fly that, when combined two by two, give rise to various shades. In plants, it is also common to see the phenomenon of polyaelia, especially in self-sterility, which does not allow self-fertilization or fertilization of individuals with a very similar genetic pattern. For example, in tobacco the pollen grain has the S 1 allele , which prevents growth in the carpels of flowers carrying the same gene. Thus, this pollen grain will only fertilize if the carpel is S 2 S 3 , S 3 S 4 , etc.
The ABO blood group system is a classic example of polyaelia in the human species.