Melanin inhibitor gene is a dominant gene. This means a non-expressing cat can not carry this gene . Offspring can receive this gene from either parent but only if one or both parent has the gene. The Inhibitor gene has a greater affect on the yellow pigment phaeomelanin than on black pigment eumelanin.

Silver vs. Smoke

Agouti cat + Inhibitor gene = Silver
Non-agouti cat + Inhibitor gene = Smoke

What is tarnish?

The Inhibitor gene removes varying degrees the yellow pigment from the hair shaft. Yellow pigment still showing through is often referred to as “tarnish” or “tarnishing”. This yellow pigment can cause a “dirty” coat look or “rust” color. Breeding silver to silver color will produce little to no tarnishing.

smoke	aa I-	-	For "I-" you can either have II (homozygous for silver) or Ii (heterozygous for silver)
silver shaded	A- I-	plus genes for tabby	For "A-" you can either have AA or Aa. For "I-" you can have II or Ii. Note that silver tabby, shaded and shell have the same genetic code for their coat colour.
silver shell	A- I-	plus genes for tabby
silver tabby	A- I- T^a- ticked	For "T^a-" you can have T^aT^a, or T^at^a. You find T^aT^a f.e. in the Somali or Abyssinian.
	A- I- Mc- mackerel	For "Mc-" you can have McMc or Mcmc. Note: You may add T^a- or t^at^a to this code.
	A- I- mcmc blotched

Resources

http://www.eurocatfancy.de/en1/nav/cat-genetics/gene_I.html

http://rfwclub.org/Silver.htm

Inhibitor Gene - Dominant Cat Trait

Silver vs. Smoke

What is tarnish?

Resources