Traits are maintained by genes. What are genes? Many segments contained in chromosomes are called genes or genetic factors. Each gene “represents” a specific feature of the body. For example, some genes are related to the color of the cat’s coat, while others relate to the length of the coat. There are also genes related to the size of various parts of the body, the function or behavior of organs in the body. Cats pass on their traits to the next generation through genes. There are many interesting aspects in cat genetics that we should learn about.
According to foreign media reports, Venus, a three-year-old cat, jumped into the Internet. Half of her face was pure black with green eyes, and the other half was orange with tiger stripes and blue eyes. How can a cat grow like this?
Many scholars say that this strange kitten is a chimera. In mythology, chimeras are unique monsters made up of the body parts of different animals. Feline chimeras are somatic cells in the body that contain two different types of DNA molecules, which are formed by fusion of two embryos. Chimeras are not uncommon in cats. In fact, most male kittens are chimeras. If a kitten has a distinct mottled orange and black coat, it has an extra X chromosome. But for female kittens, there are already two X chromosomes, so it is impossible for female kittens to have extra X chromosomes. This means that this kitten named Venus can’t be a chimera.
So, if you want to find out why, you need to use genetic methods. A cat has 19 pairs of chromosomes, one from the mother and one from the father. Genes are arranged on these chromosomes, and they provide the information necessary to produce a cat. All the genes on all chromosomes make up the genome, the complete genetic template of a cat. Each gene has a specific location on the chromosome, so a gene can also be called a “locus”. So every cat gene has an allele, from the father and from the mother. The genotype of each locus is determined by these two alleles. For example, in a long haired cat, the genotype of the long hair locus is “ll”, which is called homozygous.
Although the 19 pairs of chromosomes in the cat’s nucleus are the same, there is a slightly different pair of chromosomes. This is the chromosome that determines the individual’s sex. The female contains a pair of “X” chromosomes, which are represented by “XX” symbol, while the males contain an “X” and a “Y” chromosome, so they are called “XY” chromosomes.
When cats reproduce, two cells from different individuals, the egg and the sperm, combine together. Unlike other cells in the body, the nucleus has only one set of chromosomes, not two pairs of chromosomes. This means that when an animal is pregnant, the two groups combine to form a standard pair of chromosomes again. The single sex chromosome of male sperm can be “X” or “Y”, while that of female egg is “X”. Therefore, the sex of a kitten depends on whether the first contact with the egg is x or Y sperm. If it is Y sperm, it combines with the egg X chromosome to form a male XY pair. After the egg and sperm combine, the two sets of chromosomes are combined in the nucleus of the recipient egg.
Each type of germ cell has its own gene, and the paired chromosomes contain genes for sperm and egg. However, in a slightly different order, the thermoelectric power plant forms a string of chromosome “beads”. It is these rearranged genes that make the fertilized egg and the resulting cat unique. The genotype of a short haired cat can be derived by observing the phenotypes of its offspring from mating with a long haired cat. Such mating is called test crossing.
The color of cat’s hair, skin and eyes comes from melanin. Melanin particles precipitate in the hair stem, and their shape, size and arrangement affect the color of the fur. There are two different types of melanin: eumelanin and palmitonin. It is generally believed that eumelanin is spherical and absorbs almost all light, so it is black; brown melanin has a slightly longer shape, which is rugby like and reflects light in the range of red, orange and yellow.
The color of most cats’ fur is hardly affected by the environment. However, there is an interesting exception: Siamese allele (CS) of albino locus can make the expression of pigment sensitive to temperature. Siamese genes encode a temperature sensitive tyrosinase that inactivates at the cat’s core temperature, giving the cat a light brown background. However, the enzyme is active at the end of the limb, which is much lower in temperature. It can synthesize normal amount of pigment and give Siamese cat a unique dark “tip”. In fact, “indoor” Siamese cats living in warm places tend to be lighter in color than their “outdoor” siblings, who get quite dark hair in cold winters. CB allele is also temperature sensitive, but the effect is weaker than CS, so the coat color expressed by CB allele is also darker.
For Venus, the cat mentioned above, there is a theory that the melanin gene is activated in all cells on one side of the cat’s face and orange on the other side. As the kitten develops, these two areas of different coat color meet at the midline of her body. So two faces of different colors were formed, but it was also found that the kitten had a unique blue eye. Cat eyes are usually green or yellow, not blue. At present, geneticists are powerless to solve this problem. However, it is believed that with the development of science and technology, more genetic characteristics of cats will be revealed. At that time, it will not be so difficult to answer these questions.