Genetic (generalities)

Genetics is the survey of the transmission of the characters of the parents to the children's. These are the genes carried by the chromosomes that transport the hereditary characters. The discoverer of genetics was an Austrian monk, Grégor Mendel, at the end of the 18^th century. He  determined the big laws of genetics. To study the possibilities of progeny of an individual given, some things are indispensable to know :

• The phenotype : it is what one sees (example : a blue cat).
• The genotype : it is the set of the hereditary characters; the genetic card of the topic (example : a black cat, carrier of bruise).
• A gene is said dominant when its presence, brought by only one parent, is sufficient to have an effect on the phenotype, it is symbolized then by a capital letter.
• A gene is said recessive when the two parents must bring it so that it has a visible effect, it is symbolized by a minuscule letter. In this case, the genotype is in agreement with the phenotype, the individual is pure (homozygote) for this gene and, the cat doesn't hide anything for this character.
• An individual's cells contain an even number of chromosomes, half being brought by the father, the other by the mother. Among the cat, there are 19 pairs of chromosomes; if the sexual cells contained the same stock of genes that the other cells, the number of these would double to every generation. To avoid this phenomenon, the sexual cells only contain a simple stock of chromosomes, it is about the spermatozoids and ovums. The meeting of two sexual cells gives back an individual to double stock of chromosomes.

For example

Parents : II

II double stock of chromosomes

simple stock

cells sexual I I

I I of chromosomes

double stock

II children

II of chromosomes

The determination of the sex of the kittens is made by the father : the male possesses 18 pairs of autosomic chromosomes and a pair of sexual chromosomes XY. It is while giving X or THERE that the male determines the sex of the kittens; the female possesses 18 pairs of autosomic chromosomes and a pair of sexual chromosomes XX, she can only give X.

For example :

Parents : female XX, XY male

Cells sexual X XS, X

Children; Female XX, male XY

In most studies of the genes concerning the color of the cat, the sex of the parents as kittens won't be taken into account. Only the survey of a gene bound in X should take (the Orange gene, that gives the redhead cats or scales) into account the sex of the topics.

A given gene will always have the same function and the same place on the chromosome to which it is attached, this place is called the locus. To the same locus a gene is that a precise action has but that can have several versions : A+ example, presence of hairs agoutis (clear hairs scratched of dark)", TO" all hairs is dark. The dominant gene of the set is symbolized by a capital letter, its recessive versions by the same minuscule letter, for example : A+, has, the gene that gives the wild expression that often permits the best camouflage in the nature, is accompanied by a" + ".

Other example :

Locus

ex : Homozygous A+A+

chromosome

or A+a hétérozygote

or homozygous aa

Remark : when the topic expresses on its phenotype the action of a dominant gene, one cannot know if it is homozygous (pure) for this gene. On the other hand, if it expresses the action of a recessive gene, one is sure of the homozygotie.

As good to know a few definitions :

• Carrier : individual containing heterozygote in its genetic stock, for example, a recessive gene.
• Chromosome : minuscule structure in the shape of short stick situated in the core of the cells and that controls the hereditary characters. It is there that are the genes, disposed in linear order. Every living being possesses a stationary number of chromosomes, feature of the species.
• Core : center of command of the cell; contains the chromosomes (DNA).
• Counterparts (chromosomes) : chromosomes matched, each coming from one of the parents.
• Dominance : situation in which one of the chromosomes of a pair of allèle expresses itself completely (total dominance) or partially (partial dominance), while the other is genetically silent. The term also applies to the feature produces by a dominant gene.
• Enzyme : big molecule, of nature completely or partially protéique, that adjusts or provoke a transformation (of metabolic type).
• Gamete or germ-cell : sexual cell destined to merge with the gamete of the other sex at the time of the sexual reproduction. The ovum is the female gamete, the spermatozoid is the male gamete.
• Gene : the gene is the particular segment of DNA, situated on the chromosome : unit of the heredity, controling the growth, the development and the working of the organism.
• Genetic link : grouping of different genes on the same chromosome, near enough physically to be transmitted like only one entity.
• Genetic pool : genetic equipment of an individual given, in relation to the considered characters.
• Genotype : it is the set of the hereditary characters; the genetic card of the topic (example : a black cat, carrier of bruise).
• Heterozygote : for a given genetic character, says itself of an individual or a cell possessing two different genes received each of the parents. The pair of allèle is composed thus of a dominant gene and a recessive gene.
• Homozygote : for a given genetic character, says itself of an individual or a cell possessing two identical genes within a pair of allele.
• Hooked (ears) : ears bent toward the before. This phenotype results from the effect of a dominant gene that alters the structure of cartilage. It must not be at a true Korat.
• Inbred (crossing) : the cats are mated between direct or very near (parent-child or brother-sisters) parents. These crossings must be the object of a lot of attention and must require good knowledge in genetics.
• Inhibitory (gene) : one thinks that this gene is responsible for the inhibition of the color; he would be therefore person responsible of the tipping and varieties silvered among some races of cats (ever at the Korat).
• Letal (gene) : gene whose phenotipical effect is so radical that it drags the carrier's death. Various letal genes can provoke the death to different stages of the development, since the fertilization until an advanced age. These genes can be dominant, partially dominant or recessive.
• Locus : position occupied site on a chromosome by a gene or one of its alleles (plural : loci).
• Modifiers : polygènes altering the effect of a major gene.
• Mutation : sudden modification of the genotype, without report with an individual's ancestry.
• Nucleotidic basis : a gene is composed of the sequence of four nucleotidic basis : the adenine (TO), the guanine (G), the thymine (T) and the cytosine (C). The matching is strict : To with T; G with C. The different possible combinations constitute the genetic messages that are expressed as a molecule of RNA says messenger, who is deciphered in the cell at the time of the synthesis of proteins.
• Partial or total dominance : state heterozygote where the phenotype is intermediate between the one of the two homozygotes.
• Pedigree : the family tree of an animal given; the document attesting its origins.
• Phenotype : physical appearance of a dependent individual of its genetic equipment (genotype).
• Polygene : together of two pairs of alleles (or more), with a presumed cumulative effect, governing quantitative characters as the size, the pigmentation, intelligence. If their working is simultaneous, a small group of genes can produce specific physical characters.
• Recessive : designate a gene that, within a pair of alleles, don't express himself (because of the presence of the dominant allèle). This term also applies, by extension, to the character controled by the gene. Normally, the recessive genes can express themselves that to the homozygous state.