A dominant gene is the gene that is expressed (shown).
Dominant genes are written in capital letters.
An example of a dominant gene is the inhibitor gene which causes cats to be silver.
II= the cat is silver, all offspring will be silver
ii= the cat is not silver, no offspring will be silver
Ii= the cat is silver, offspring may be silver
Recessive genes are not expressed when dominant genes are present but are only shown when both genes are recessive. However they can be carried and show up in future generations.
Recessive genes are written as lower case letters.
This is an example with the Seal Lynx Point (Blue Eyed Snow)
C= not Snow
CC= the cat is not Snow, no offspring will be Snows
cscs= the cat is Snow, offspring may be Snows
Ccs= the cat is not Snow, offspring may be Snows
Kittens will have one gene from their mother and one from their father.
So if a Snow (cscs) mates with another Snow (cscs) all the kittens will be cscs therefore Snows.
If a Snow (cscs) mates with a Brown that carries for Snow (Ccs) some of the kittens will be cscs and Snows and some will be Ccs and not Snow.
If a Brown which doesn’t carry for Snow (CC) and a Snow (cscs) mate all kittens will be Ccs, therefore not Snows. Of course these kittens (Ccs) will all be carriers of the Snow gene, so their offspring could be Snows.
Homozygous & Heterozygous genes
A Homozygous gene has two alleles the same i.e. aa, AA, dd, II, ii.
A Heterozygous gene has two separate alleles i.e. Dd, Aa, Ii.
If a cat has a heterozygous set of genes the dominant one will overrule the recessive.
If we take the genes for creating the Blue coat colour you can see what I mean.
Remember that capital letters are dominant and lower case is recessive.
D= Dense colour (not Blue)
d= dilute colour (Blue)
DD= the cat is not Blue, no offspring will be Blue
dd= the cat is Blue, offspring may be Blue
Dd= the cat is not Blue, offspring may be Blue
Genetic testing can be carried out on cats. Langford Laboratory carries out genetic testing in the UK and UC Davis carries out testing in the US. This enables breeders to find out what colour genes their cat holds before breeding him/her as well as finding out for sure which kind of Bengal they have – this can sometimes be difficult in the case of Snows for example. Currently there is no test for the marble gene or the Silver gene.
Genetic testing can also be useful for genetic cat diseases and finding out if your cat is a carrier or affected by a particular gene.