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Solution #3: When a black cat (D?) with an unknown gene is bred with (crossed with) a blue grey cat (dd), then all cats will get at least one "d" from the blue parent. If all of the kittens are black, and none of the kittens have blue-grey colour, then the black parent must have only given "D" genes to its kittens. This would mean the black D? must have DD genes.

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Bibliography

Figure 1 show genetic inheritance of colour when mating DD and dd parents. All the kittens look black

1. Understanding Cats Their History, Nature and Behavior. Robert Tabor. David and Charles Publishers 1997

2. Good Owners Great Cats A guide book for humans and their Feline companions Authors Brian Kilcommons Sarah Wilson Warner Books Inc. Nov 1995.

3. The book of the Cat Editors Micheal Wright and Sally Walters. Pan Books 1980.

4. The Complete Cat Owner's Manual. Author Susie Page. Fog City Press 2004.

Now, suppose you have a black cat but you don't know what genes it carries. It must have at least one D gene to look black. It's second gene could be a "D" or a "d". One way to figure out the gene that this black cat has is to do a breeding experiment.

If you breed your black cat called D? with another cat that is "dd"-blue grey, the kittens will tell you what their parents' genes are.

Figure 2: The result of crossing a black cat (parent carrying an unknown gene D?) with a blue grey parent (dd). Some cats are blue grey.

Figure 2 shows proof of inheritance of genes from a black and a blue parent where blue kittens occur.

Solution #1: When a black cat (D?) with an unknown gene is bred with (crossed with) a blue grey cat (dd), then all cats will get at least one "d" from the blue parent. If some of the kittens have blue-grey colour, then both parents must be carrying the "d". This would mean the black (D?) parent must have Dd genes.

Figure 3 shows the result of breeding a black cat with unknown genes to a blue parent where all the kittens are black.

Imagine you have a pure breeding black cat that mates with a pure breeding blue (grey) cat. A pure breeding cat will give away the gene for its colour, which is "D" for dense black or "d" for a dilute colour which turns into a grey blue.

Figure 1: This figure show the mating of a DD & dd parents. All the kittens look black.

If the DD and dd cats mate, their babies must get a colour gene from each parent. This means that all kittens will carry Dd genes. Because the D (dense-black) dominates over the "d" dilute, the kittens will all look black even though they carry (or hide) the dilute gene.

All traits are controlled by genes. This means that there is a different gene for hair colour, eye colour, hair length, and so on.

To be technically correct, the above colours, "D" and "d" are called allelles that rest in a specific gene. There are often many allele choices for a single gene. The genetic inheritance of hair colour in the cat is pretty complicated to figure out, because some of the alleles can play tricks on the appearance of the colours. The important point is that genes control traits and certain combinations of genes and their alleles make the specific breeds of cats.