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Gene XY: Sex

 
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Genetic terms in cats
Genome of the cat
Dominance of genes
Cat Breeding techniques
Crossing Table 1
Crossing Table 2
Crossing Table 3
Gene A: Agouti
Gene B: Black
Gene C: Full colour
Gene D: Diluted
Gene Dm: Dilute modifier
Gene Fd: Folded ears
Gene I: Inhibitor
Gene L: Shorthair
Gene Mc: Mackerel
Gene O: Orange
Gene S: Piebald spotting
Gene W: White
Gene XY: Sex
Quality Points for Cats

 

Gene XY: Sex

 

Chromosome X, Y

Male

The male has a pair of different chromosomes: XY.

Female

The female has a pair of equal chromosomes: XX.

Possible combinations

  male
  X Y
female X XX
female
XY
male
X XX
female
XY
male

 

How are these combinations of genes done ?

Let's stick to the above table of possible combinations.
Each gene is represented in a pair. The gene pair of the male was XY, that of the female XX.
Each parent gives 1 half of its gene pair to its litter, both the female and the male. Often you may hear that the male is more important at the mating, that's not true when it comes to heredity, both the female and the male pass one half of each gene pair to their offspring. But the male may play an important role when you look at a cat population where the male is used as stud male, he can sire more females than one female may have litter.
Now we split the pair of each parent into its 2 parts:

The male gives either X or Y to his offspring.
X
Y
The female gives either X or X to her offspring.
X
X
Out of these parts of each parent we build all possible combinations.
That reading is easier, we always put the gene pairs in alphabetical order.
  • X (first half from the male) plus X (first half from the female)
  • Y (second half from the male) plus X (first half from the female)
  • X (first half from the male) plus X (second half from the female)
  • Y (second half from the male) plus X (second half from the female).
XX

 

XY

 

XX

 

XY

 


If we have more than one gene pair we start with the last pair varying and build all combinations. Then we vary the second last pair and build all combinations, and so on.
Let's show this on an example: a cat might have Bb Dd.
Split now each pair into its 2 parts:
1st pair into B and b, 2nd pair into D and d.
We keep the 1st part of the 1st pair fixed and vary the parts of the 2nd pair:
the cat can pass BD or Bd.
Now we keep the 2nd part of the 1st pair fixed and vary the parts of the 2nd pair:
the cat can pass bD or bd.
Therefore the cat can pass the following combinations: BD, Bd, bD, bd.

For those who are interested in calculating the amount of possible combinations:
If n is the amount of gene pairs, then there are 2n combinations possible.

 
[A] [B] [C] [cb & cs] [D] [Dm] [Fd] [I] [L] [Mc] [O] [S] [W] [XY]

 
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