Examples of Multiple Alleles

 Several cases of multiple alleles and pseudo alleles are known both in animals and plants. Some well-known cases of multiple alleles include

(1) Fur color in rabbits

(2) Wing type in Drosophila

(3) Eye color in Drosophila

(4) Self-incompatibility alleles in plants

(5) ABO blood group in man, etc.

Now it is believed that most of the genes have multiple alleles if in-depth investigations are made.

Fur Colour in rabbits

The fur color in rabbits is a well-known example of multiple alleles. In rabbits, the fur color is of four types viz., agouti, chinchilla, Himalayan, and albino.

i. Agouti- This has full color and is also known as wild type. This color is dominant over all the remaining colors and produces agouti color in F1 and 3:1 ratio in F2 when crossed with any of the other three colors in rabbits. This color is represented by C.

ii. Chinchilla- This is lighter than agouti. This color is dominant over Himalayan and albino and produces chinchilla in F1 and 3:1 ratio in F2 when crossed with either Himalayan or albino.

This is represented by cch.

iii. Himalayan- The main body is white while the tips of the ear, feet, tail and snout are colored.

This color is dominant over albino and produces a 3:1 ratio in F2 when crossed with albino.  This is represented by ch.

iv. Albino- This has pure white fur color and is recessive to all other types. This is represented by c.

2. Wing type in Drosophila

In Drosophila wings are normally long. Because of mutations at the same locus in different flies, vestigial (reduced) wings and antlered (less developed) wings were developed. Both vestigial and antlered are alleles of the same normal gene and also of each other and are recessive to the normal gene.

Suppose vestigial is represented by the symbol ‘vg’ and antlered wing by ‘vga’. The normal allele is represented by the symbol +.

Thus, there are three races of Drosophila

Long ++ (+/+)

Antlered vga vga (vga/vga)

Vestigial vg vg (vg/vg)

A cross between a long-winged normal fly and another having vestigial wings or antlered wings is represented below: