Cats ... Pets of many people. Someone likes redheads, some black, some mosaic. Others are attracted by Persians, Siamese cats or Egyptian cats. This is all a matter of taste.
However, the color of the animal, its exterior, character, disease, pathology, mutation depend not only on the breed or lifestyle, but also on the chromosome set (primarily on it), which is constant and specific.
And yet, how many chromosomes does a cat have, what is their number and function? This will be discussed below.
Genome and chromosomes
Talking about how many chromosomes a cat has is extremely difficult without a basic knowledge of genetics.
The genome is a structure that contains genetic information about the body. Almost any cell contains a genome. But the chromosome contains all the information about the structure of the cell. The chromosome is a nucleoprotein structure in the nucleus of a eukaryotic cell. The chromosome contains a significant part of the hereditary information that is stored, implemented and transmitted to the future generation.
A chromosome is a cell nucleus structure consisting of deoxyribonucleic acid (DNA) and proteins. It is worth recalling that DNA is a macromolecule that provides storage, transmission from generation to generation, and the implementation of a genetic program for the development of a living organism.
There are two types of chromosomes in different organisms:
Eukaryotic type - characteristic of living organisms (eukaryotes), whose cells contain the nuclear membrane, DNA molecules in the nucleus and mitochondria.
Prokaryotic type - found in organisms in the cells of which there is no nuclear membrane, and DNA molecules are enclosed in histones (prokaryotes).
Externally, the chromosome is similar to a long thread with strung beads, each of which is a gene. In addition, the gene is located on its strictly fixed region of the chromosome - the locus.
The number of chromosomes in animals
How many chromosomes are there in cat cells? Any living organism has homologous or paired chromosomes and haploid or unpaired (sex) chromosomes. The latter include the egg and sperm, they have a set of XX and XU, respectively. When dividing, they decompose into X, X and X, U. Depending on the new combination of the pair in the fertilized cell, the sex of the new organism (in our case, the kitten) will be determined.
To the question: “How many chromosomes are there in cat cells?”, Genetics gives an exact answer. In a domestic cat, the chromosome set includes 19 pairs of chromosomes (18 paired and 1 unpaired: XX for females and XU for males). The total number of chromosomes in a cat is 38.
In other animals, the number of chromosomes is invariable and individual for each species (for example, in dogs - 78 chromosomes, in horses - 64, in cows - 60, in hare - 48). Recall that in humans the number of chromosomes is 46.
Karyotype and cat chromosome complex
A karyotype is a pair of chromosomes with a specific number, size and shape for each animal species. The signs of each type of living organism are inherited by karyotype. For example, the presence of a trunk in elephants may be a karyotypic sign. The birth of an elephant calf without a trunk will be a deviation from the karyotypic norm, that is, a pathology.
All cells are paired, the future appearance, exterior, color, and character of the cat depend on them. The last - 19 pair contains sexual information and half of the chromosome set. In the process of fertilization, both parts combine to form a complete cell.
Cat ovum chromosomes
What set of chromosomes does a cat's egg have? The somatic cell of a cat has 38 chromosomes, which are diploid cells. An egg is a sex haploid cell. Accordingly, 38 needs to be divided into two, we get 19, that is, there are nineteen chromosomes in the cat's egg cell.
The inheritance of cats
The somatic cell of a cat has 38 chromosomes that contain DNA molecules with genotypic information. Genotypic manifestations that are reflected in the external appearance of a living organism are called a phenotype. Phenotypic manifestations of kittens vary in color, size of the animal.
The genes of the offspring are paired - one gene from the female, and the other from the male. As you know, genes are divided into dominant (strong) and recessive (weak). Dominant genes are indicated in uppercase, Latin letters, recessive - lowercase. Depending on their combination, homozygous (AA or aa) and heterozygous (Aa) types are distinguished. The dominant gene is manifested both in the homo- and heterozygous state. The recessive gene will show its signs only in the homozygous type (aa). This genetic knowledge is useful in calculating the signs of future kittens by the phenotypic manifestations of their parents. Here it is important to know which gene responsible for the manifestation of a particular trait is recessive or dominant.
Coloring genes of animals are located on the X chromosome, they are presented in the table below:
| a | Gray |
| b | Chocolate |
| c | Platinum purple |
| d | Redhead |
| e | Cream |
| f | Tortoiseshell |
| g | Tortoise blue cream |
| h | Tortoise chocolate |
| j | Tortoise lilac |
| n | The black |
| o | Sorel, honey |
| p | Tan |
| q | Tortoise red brown |
| r | Tortoise Tan |
| s | Smoky |
| w | White |
| y | Gold |
| x | Unregistered color |
Inherited characters
Cat chromosomes transmit to the offspring certain hereditary traits, such as:
- ears - their location and dimensions, the size of the auricle;
- wool - the color and nature of the pile;
- eyes - pigment color;
- tail - its length, thickness;
- illnesses.
Breeders cull weak and defective individuals so that subsequent offspring are stronger, healthier and more perfect.
Wool color
In a thousand cat genes are those that are responsible for both their color and mutation, leading to a change in the color and structure of the coat. The asexual somatic cell contains mutation elements in the proto-oncogen by the color of the coat, which inhibits the migration of melanoblasts. Therefore, the latter cannot get into the skin, and the pigment, accordingly, does not reach the hairline. This explains the white coat of the animal.
Some melanoblasts manage to get into the hair sacs on the cat's head, then colored spots appear on the fur. These cells may well reach the retina of the eye: with a small number of melanoblasts, the eyes turn blue, and with a large number, the pupils in the animal will be yellow.
The same chromosome is also responsible for coat color. The usual structural form of melanoblasts gives the striped color of the animal. There are also semi-dominant changes, for example, in the Abyssinian tabby. Homozygous individuals have no stripes, the color is homogeneous, and heterozygous individuals with such a mutation differ in stripes on the muzzle, legs, and tail. In the case of a recessive change, the transverse stripes on the animal's hair are deformed into irregular lines on its back, manifesting itself in powerful black longitudinal stripes.
A gene mutation that affects the tyrosinase enzyme leads to albinism. This happens not only in cats, but also in other mammals.
Tyrosinase decreases its activity depending on the temperature of cats - the lower it is, the more active the enzyme. In such cases, there is intense staining of the peripheral parts of the body: the nose, the tips of the legs and tail, the ears of Burmese cats.
Mosaic cats
The set of chromosomes of a cat responsible for coloring is localized on the X chromosome. Mosaicity of cats is not uncommon, but still three-colored cats are less than two-colored cats.
In this case, the color is determined by the alleles of the O gene:
O - affects the yellow (or red) color of the fur;
o - responsible for the black color.
Tortoiseshell cats are heterozygous for this gene; their genotype is Oo.
Yellow and black spots in them develop as a result of accidental inactivation in the early embryogenesis of the X chromosome by the O or o allele. Cats can only be homozygotes for this trait (OU - red or OU - black).
Tortoiseshell cats are extremely rare - they are characterized by the chromosomal constitution of XXV and the OoU genotype. This is due to the rare birth rate of mosaic cats (or cats of tortoiseshell color).
Inheritance of tricolor cats:
Color black - gene XB - genotype - XB XB; HVU;
Red color - Xb gene - genotype - XB Xb; XU;
Color tortie - gene - XB; Xb - genotype XB; Xb.
White color cats
White color at the chromosomal level is the absence of pigment. Pigment cells are blocked by one gene - W. If recessive traits of this gene (ww) are present in the genotype of cats, then the offspring will be colored, and if there is a dominant trait (WW, Ww) and there will be many other designations of gene chromosomes in cats' genome (BOoSsddWw ), then we will still see a completely white cat. However, such cats can carry both spotting and drawing, but only if the offspring does not inherit the W gene.
Chromosomes of a cat with Down syndrome
This disease is found not only in humans, but also in animals, cats are no exception.
On the Internet, there are many stories and photographs from the life of such animals. Like humans, such animals may well live and be active, but visually they are different from healthy ones. Like people, such animals need some care, care and treatment.
To the question: “How many chromosomes does a Down cat have?”, One can definitely answer: 39.
Down syndrome occurs when another extra chromosome appears in the gene set of chromosome molecules - odd. In the case of cats, this is the 39th chromosome.
A cat with an extra chromosome in nature is rare for the simple reason that the animal does not use drugs, does not drink alcohol, does not smoke, i.e. the provoking causes of a gene mutation are excluded. But still, this is a living organism, sometimes it also has failures.
Scientists and biologists do not have a definite opinion about the extra chromosome. Some say that this cannot be, others say that it can, and still others say that this occurs when the animal is artificially bred as an experimental subject.
A cat with 20 chromosomes (the twentieth pair of chromosomes is superfluous) occurs, but it has almost no chance of reproducing healthy offspring. This, of course, does not mean that such an animal cannot be loved. They are quite cute, but a little unusual, different, but still they are alive. For example, a cat with this syndrome (Maya from America) has become the favorite of its owners (Harrison and Lauren). They created their Instagram page for the cat, regularly posting their photos and videos. Maya has become a favorite of Internet users, she is quite active and cheerful, although she suffers from shortness of breath and constantly sneezes. But no one bothers her to live for her pleasure and for the pleasure of her masters.
By the way, do not confuse Down's cat syndrome with genetic mutations that lead to a physical change (deformation) of the faces of the animal. This is more common in nature than Down's disease, and is due to crossbreeding between relative cats (intergeneric crossbreeding). If there are many animals of the same genus in the offspring, then sooner or later physiological changes will occur not only in the appearance of the animals, but will also affect their development as a whole. If breeders can control it, then the owners of cats running around the yards can hardly track it. Some people throw such offspring, while others, on the contrary, are philosophical about this and also love their pets.
How many lives does a cat have?
Everyone knows that in 1996 the first cloning was carried out in the world (the famous sheep Dolly). Five years later, scientists cloned a cat, gave it a name - Carbon Copy (in Russian) or Carbon Copy (this is Latin).
For cloning a cat of a tortoise gray-red color was taken - Rainbow. Eggs and somatic cells were removed from the ovaries of the Rainbow. Nuclei were removed from all eggs and replaced with nuclei isolated from somatic cells. Then, electroshock stimulation was performed, and then the reconstructed eggs were transplanted into the uterus of the gray tabby cat. It was this surrogate mother who gave birth to Carbon Copy.
But Carbon did not have red spots. During the study, it was possible to find out the following: in the genome of a cat (female) there are two X-chromosomes that are responsible precisely for the color of the animal.
In the fertilized cell (zygote), both X chromosomes are active. In the process of cell division and further differentiation in all cells of the body, including future pigment cells, one of the X chromosomes is inactivated (i.e., activity is lost or greatly decreases in the cell). If the cat is heterozygous (for example, Oo) according to the color gene, then in some cells the chromosome carrying the red allele may be inactivated, in others it may carry the black allele. The daughter cells strictly inherit the state of the X chromosome. As a consequence of this process, tortoise coloration is formed.
When a cat was cloned in the nucleus of a reconstructed egg cell, extracted from an ordinary somatic cell of a tricolor cat, complete deactivation (restoration of viability or activity) of the switched off X chromosome did not occur.
Full reprogramming of the nucleus of chromosomes during the cloning of a living organism (in this case, cats) does not occur. It is likely that this is why cloned animals get sick and can not always bring healthy offspring. The carbon copy is still alive. She became the mother of three adorable kittens.
Conclusion
This article examined how many chromosomes a cat has, what they “are responsible for” and how they affect an animal.
To the question: “How many chromosomes are there in a cat's egg?”, The answer is unequivocal - 19 chromosomes. The color genes of cats are located on the X chromosome. Melanoblasts (i.e. cells that give rise to pigment cells producing melanin) do not yet contain pigment and are responsible for the pattern on the fur coat and for the color of the iris of the eyes. The tyrosinase enzyme is responsible for the manifestation of albinism, but this enzyme should not be confused with the W gene (gives a white coat color).
Mosaic cats have the chromosomal constitution of XXV and the OOU genotype, so they are not so common. The allele (site) of the gene for mosaic cats is Oo, it is he who is responsible for the mosaic coloring.
In the chromosome set, malfunctions or mutations of genes sometimes occur, then either cats with Down syndrome or cats with a deformed appearance are born. The second can be predicted, but with the first it is much more difficult. Perhaps because this phenomenon is not the most common and there are not so many studies of its causes.
A cat, like any other living organism, can be cloned, and, as practice shows, such animals are quite viable.
In general, genetics is a very interesting and informative science that studies the laws of heredity and variability, transmitted from parents to descendants. Having deciphered the genes of an animal, you can understand what kind of offspring it will have, you can exclude gene mutations, breed pure breeds. And the motto of cat breeders: "Pure breeds - healthy cats."