You have a cat who has the black dominant gene and the blue recessive gene. If this cat mates with a cat carrying the black dominant gene and the blue recessive then:
As a rule you would expect to get more black kittens than blue kittens because black is dominant over blue.
Black Kittens- 75% Chance
Blue Kittens- 25% Chance
You can use this meathod with other cat colors and other sets of genes.
Not all of he cat's characteristics are passed on in as clearly a dominant or recessive form. Some dominant characteristics, for example, will only show up in a cat's appearance if there is another gene present to activate that specific gene, while other characteristics are gender linked. An example of gender-linked traits is the Calico Rule, or the Tortoiseshell Rule.
The ginger colour of cats, known as yellow, orange or red, is caused by the "O" gene. The O gene changes black pigment into a reddish pigment. The O gene is carried on the X chromosome. A normal male cat has XY genetic makeup; he only needs to inherit one O gene for him to be a ginger cat. A normal female is XX genetic makeup. She must inherit two O genes to be a ginger cat. If she inherits only one O gene, she will be tortoiseshell. The O gene is called a gender-linked gene because it is carried on gender, or sex, chromosomes.