Of course, if you want to understand how coat colors are inherited in dogs, you cannot avoid studying the basic concepts of genetics a little more.
Do you want to know more about coat colors in dogs?
Here you can find an overview of all color balls in dogs.
DNA – the individual blueprint
You can find them in the nucleus of every cell in your dog DNAwho are known to is in the form of a double helix.
The entirety of the DNA sequence of an organism is called its Through or heritage designated.
It is rather impractical for the cells to organize a single, insanely long DNA thread in a sensible and space-saving manner (bIn humans, the DNA of a single cell nucleus in one piece would be almost 2 meters long).
DNA is therefore in higher living beings as well as in the dog in individual Chromosomes been separated and packed compactly.
Dogs have 78 of these chromosomes.
In the human genome there are 46 chromosomes, in horsetail (yes, the plant) there are 216, in cats 38. The number of chromosomes in each species results from the history of their origins and does not say anything about the information content on the DNA.
The genetic information of an organism is recorded on the DNA.
In certain sections of DNA, the Genes, is written in a code that the body can read, showing how it can build all the proteins necessary for life when needed.
Genes control all aspects of life through the blueprints they contain, including coat color.
All sorts of different proteins are required for pigment cells to function normally, form pigment molecules and release them into the hair.
All dogs normally have the same genes on their chromosomes.
But obviously different dogs differ optically from each other.
Mutations in the blueprint can result in different variants of the same gene. In different dogs, very different gene variants can be stored at the same gene location.
Statements like “This dog has the merle gene!“So are wrong.
All Dogs have the “merle gene”. But not all dogs have exactly one of the gene variants with the blueprint for the Merle drawing (M). Many dogs have the blueprint for “non-merle” (m) on the merle gene. “Merle” and “non-merle” are just variants of the same gene.
In all dogs, the same genes are usually always present on the same chromosome (but with different information content depending on the gene variant).
As Genocide (= Gene location) denotes the position of a gene or certain DNA segment in the chromosome set. The terms ‘gene’ and ‘gene locus’ can be used synonymously in our case.
Example: A dog is on Merle-Lokus or short M-Lokus „M/m“.
What is important for us:
The dog’s body has two copies of each gene: one on the chromosome inherited from the father, one on the chromosome from the mother.
A dog can therefore only have two of the many possible gene variants of a gene locus.
Here you can find a list of all known color genes in dogs.
Mutations in the genome can lead to different variants of the same gene occurring in the gene pool of a species. These different gene variants for the same gene locus are called its Allele designated.
Different alleles can lead to a difference in the expression of a trait (e.g. merle or non-merle).
The listing of all known alleles for a gene locus is called its Allelserie or Allelreihe designated. There are more than two different variants at many gene locations. A dog can only have two of these many possible gene variants per gene location!
Letter abbreviations are used to represent a genotype. The alleles of the same gene locus all have the same letter.
Am Agouti-Lokus or short A-Lokus For example, there are four alleles, for which the following abbreviations are common:
The allele Ay is short for Ayellow (Zobel).
The allele aw is short for awildtype (Agouti).
The allele at is short for atanpoint (Tanmarken).
The allele a is short for recessive black.
- As “Wild type“Is the name of the gene variant for the original normal form from which the other variants of a gene locus have been derived through mutations (aw).
- The alleles that result from mutations of the wild-type allele are called Allele mutant denotes (Ay, at, a).
The capital letter is used for the dominant allele of an allele series. The lower case letter is used for subordinate ranks.
This is how allele series can be represented in a simplified way:
B-Lokus → B (schwarz) > b (braun).
A-Lokus → Ay (Zobel) > aw (Agouti) > at (Tanmarken) > a (Recessive black)
If you are concerned with the inheritance of colors in dogs, you cannot avoid memorizing the names of the individual gene locations, their possible alleles and the respective doinic sequence in the long term!
Homozygosity and heterozygosity
As a reminder: Of all the alleles known for a gene locus, a dog can only have two of these gene variants, one from each parent.
- If a dog inherits the same allele from both parents, it is for this trait pure or homozygot.
- If a dog inherits a different allele from each parent, it is for that trait mischievous or heterozygot.
If a dog is heterozygous for a trait, the dominant allele is written first, e.g. B/b instead of b / B.
Different spellings with or without separators are equivalent (B/b = BB).
If you are only sure about one of the alleles, you also write “B/-„.
Laboratories report in their test results whether a particular mutation was found or not. For spellings like “+/–“(” + “For the wild type) or”at/N”(“ N ”for“ not found ”) information material is usually made available with which this spelling can be interpreted correctly.
Genotype and phenotype
The listing of the genetic makeup of an individual is called it genotype: KB/kY B/b (dominant black, wears brown) or kY/kY AY/at (Sable, wears tan marks).
The visible appearance of an individual, on the other hand, is considered to be his Phenotype designated. Here the visible appearance is described, eg a dog is “black with tan-colored markings” or “brindle with mask”.
This can be confusing with the dog’s coat colors, as breeders of different dog breeds describe the phenotype differently (sable = fawn = sable = fauve). Or rewrite it right away, but mean something completely different. If someone says their dog is “red”, it gives little information about the genome type.
Dogs with the same genotype can look different
On the one hand, many fur drawings are subject to a certain degree Random factor (e.g. Merle, Stromung, Ticking, Piebald). On the other hand Often other factors influence the exact characteristic expression (unknown modification genes, etc.).
Take a look at the following littermates, for example. All are sable with flow and mask (Em / – kbr / – Ay / -). But not all look the same:
Not all similar dogs have the same genotype
Some colors and patterns see themselves even to the trained eye confusingly similar. also different drawings are superimposedso that you can often only see a fraction of the possibilities in the phenotype.
For example, white spotting overlays all other colors. So an unpigmented dog could be genoytpically brindle or merle or both, you wouldn’t tell.
Inheritance, dominance and epistasis
Owns a dog at the same location two different alleles, both alleles are usually not expressed to the same extent. Alleles at the same gene location can mutually influence each other in terms of their expression. One also speaks of Dominance.
A dominant Allel leads to the suppression of the characteristic expression of a recessive allele.
Dominance does not usually mean that an allele is actively having the effect of a weaker allele suppressed. Often times it is simply that recessive alleles compared to the dominant one Wild type have lost part of the information on their blueprint due to mutations.
But if the dog still has at least one allele with the blueprint for a functioning protein, then one copy is sufficient to express the trait. But if a dog has only inherited mutant alleles, it has no choice but to build more or less defective proteins from them.
We find a simple example of such a dominant-recessive inheritance on B-Lokus:
B stands for a functioning TYRP1 gene. TYRP1 contains the blueprint for a protein that is necessary for the formation of black pigment.
b stands for a mutation-defective variant of TYRP1.
If a dog only has b / b available, its basic color brightens to brown due to the lack of functional TYRP1.
But if a dog has at least one B allele, that is enough for the formation of normal black pigment.
B is dominant to b.
b is recessive to B.
» In some cases, mixed inheritance also leads to one intermediate inheritance. Here there is a mixed form of the characteristics. In the English-speaking world one speaks of “incomplete dominance“Or Semi-dominance.
Examples of an incompletely dominant inheritance are Piebald, Ticking or Merle. Pure-breed dogs have more of these traits than mixed-breed dogs.
Dominance does not always work quite as much according to the “all or nothing” principle as we learned in Mendel’s genetics at school. Dominance tends to move on a spectrum with gradual intermediate steps.
» Theoretically, it can also happen that in heterozygous alleles both gene variants are fully expressed at the same time and both are visibly present in the phenotype. One then speaks of one co-dominant inheritance.
There is no known example of this in dog color genetics. An example in humans is the blood type system. In people with blood group AB, there is no mixed form, but both characteristics (A + B) are fully developed.
The effects different genloki can influence each other.
If an allele at one locus suppresses the expression of traits from a completely different gene at another locus, we do not speak of dominance, but of Epistase.
» In a dog with genotype e / e, the characteristics of the K locus or A locus are not expressed. The E locus is epistatic compared to the K and A locus.
» In a dog with genotype KB / – the characteristics of the A locus are not pronounced. The K locus behaves epistatically compared to the A locus.
And here, too, there are exceptions, for example Seal and Ghost-Tan lead. So epistatic relationships don’t always work either all or nothing. One theory is that Seal fails the epistatic effect of the dominant KB allele at the K locus.
According to the genotype (E / – KB / -) this dog should actually be completely black, but it is not:
In the dog’s DNA we find the genes that contain all the information about the dog’s blueprint.
Each gene is linked to a specific locus in the dog’s genome.
Different variants of these genes of a gene locus are called alleles and together form the gene series for this gene locus. An individual can be heterozygous or homozygous for a trait.
Whether an allele present in the genotype is expressed in the phenotype depends on the dominance ratio of the individual alleles of a gene locus to one another and the epistasis between different genes.