In rabbits, four kinds of skin colour are known. Rabbits are accordingly classified as coloured (agouti), chinchilla, himalayan albino,
If homozygous coloured (CC)
is crossed with albino (caca), F1
individual is coloured showing that coloured is dominant over albino. F1
heterozygous coloured (Cca)
gives a 3 : 1 ratio in F2
When coloured (CC)
are crossed with himalayan albino (chch),
individuals are coloured (Cch).
These in turn give 3 : 1 ratio between coloured and himalayan albino. Similar relationship is observed when himalayan albino (having pink eyes and white coat colour except at the tips like nose, tail and feet, etc. which are black) is crossed with albino (Fig. 5.2). The results shown in Figures 5.1 and 5.2 indicate that C (coloured), ch
(himalayan albino) and ca (albino)
are allelic to each other.
Fig. 5.1. Inheritance of skin in rabbits from a cross (coloured x albino).
Fig. 5.2. Inheritance of skin colour in rabbits from a cross (Himalayan albino x albino).
Still another type is known in rabbits and is called chinchilla.
This colour is lighter than the wild (agouti). Coloured character is completely dominant over chinchilla. However F1
hybrids between chinchilla and.himalayan albino (cchch)
or between chinchilla and albino (cchca)
show light gray skin colour. A summary of different genotypes involved in this series, along with their phenotypes, is given in Table 5.1.
In mice, however, two different multiple allelic series are known for skin colour, one is albino series and other a black series (Table 5.2). In albino series, it was observed that wild type (grey) was dominant over all others, while heterozygous between any two of the three recessive alleles. (a, am
gave intermediate phenotype (Table 5.3). In black series on the other hand, black is recessive to all, while yellow is dominant to all. Light belly in GL
is dominant over darker belly. Black body of bL,
however, is recessive to grey body of normal individuals. Consequently, +/GL
both would have grey body and light belly (Table 5.4).