Cat Genetics: The Basics
Making a combination of two cats: nice, but what colors will the kittens get? Do they get short or long hair? How is it determined whether they will be females or males? The basics of cat genetics, explained in plain language.
To start with, it is useful to lay a foundation. The DNA of living things consists of genes that are always linked in pairs. A couple stands for a certain property, such as hair length. These genes are passed on to the young through reproduction. Of all pairs of genes, the young gets one gene from the father and one gene from the mother. Genes are always referred to as letters.
Within genetics a distinction is made between dominant and recessive genes. If a gene is dominant, it means that if you have that gene, you will always display that trait. You only need one such gene for this. If a gene is recessive, this means that you have to have two of them before that trait is expressed. You must have received this gene from both your father and your mother. You can also carry a recessive gene. to be. This means that you only have one of them. The gene will not be expressed, but you can pass it on to your offspring. A dominant gene is indicated in genetics with a capital letter and a recessive gene with a small letter.
If a cat of one trait has two of the same genes, it is the cat homozygous for that property. This is also called pure breeding: after all, we know for sure that the cat will pass on the same gene to all its offspring.
If the cat has two different genes of that trait, then it is the cat heterozygous for that property. This is also called impure breeding, because then you are not sure which of the two genes were passed on to which offspring.
To begin with, it is just as easy to explain how a kitten gets its sex. The genes for gender have the letters X (female) and Y (male). These genes are neither dominant nor recessive. A female has the genes for sex with the letters XX and a male has the letters XY. If this cat and tom cat now have kittens, they will pass these letters on to the little ones. The cat only has the letter X to give away and therefore passes it on to all the little ones. The tomcat gives half of the little ones the letter X and half of the little ones the letter Y.
This creates kittens that get the X from the mother and the X from the father: these are kittens, they have the letters XX. And there are kittens that get the X from the mother and the Y from the father: these are males because they have the letters XY.
It looks like this schematically:
The hair length
Hair length is one such trait involving dominant and recessive genes. In cats, the shorthair gene, indicated by the L, is dominant over the longhair gene, indicated by the l. So what does this mean?
This means that a long-haired cat should always have the code ll. After all, the gene for long hair is recessive and is only expressed if you have this double.
With a short-haired cat, on the other hand, it is less easy to determine what the genetic code is. We know that a short-haired cat has at least one L because she is short-haired. But because the gene for shorthair is dominant, we don’t know what the other gene looks like. If this cat still has an L she is pure smooth or homozygous smooth hair. If this cat has an l, it means she is a carrier of the longhair gene. She is then impure shorthair or heterozygous shorthair. As long as we are not sure what the second gene looks like, it is indicated with a dash. This cat will get the letters L-.
An example for illustration.
Suppose a long-haired male and a short-haired female have kittens. Then it looks like this genetically.
Seen schematically, this means the following.
As you can see, all kittens will at least be carriers of the longhair l. All kittens get this from the tomcat.
In addition, you can see that 50% of the kittens receive the shorthair L from the mother cat. These kittens will therefore be short-haired, but will carry the long-haired hair.
What is wrong with the other 50% of the kittens depends on what has to be entered on the line of the cat. This means two possible scenarios:
If the female turns out to be homozygous shorthair, this means that all kittens will be Ll or heterozygous shorthair. They all get the shorthair L from the female and the longhair L from the male. The kittens are therefore carriers of the longhair gene.
If the female turns out to be heterozygous shorthair, you will see in the diagram that half of the kittens will become Ll or heterozygous shorthair. They get the L from the cat and the L from the male. The other half of the kittens will be 11: homozygous long hair. They get the l from both the male and the female.