- 1.0: male bird
- 0.1: female bird
- Chromosome: On the chromosomes you can find among other things the gene loci for all properties and functions of an organism, e.g. the colour of the feathers. Human beings have got 46 chromosomes, whereby 44 chromosomes (the autosomes) are available in identical (homologous) pairs, i.e. 22 homologous chromosome pairs. According to this the genes located on these chromosomes exist double.
The remaining two chromosomes represent the sex chromosomes (heterosomes).
In the germ cells (i.e. the sperms and the egg cells) there is just a single chromosome set, i.e. 22 autosomes and one heterosome. If one sperm fuses with an egg cell again 46 chromosomes emerge. So, half of the chromosomes of a human being derive from the father, the other half from the mother. Thus, is is the same with the properties on those chromosomes.
- Sex chromosome (heterosome): The presence or absence of specific genes on the sex chromosomes generates the occurrence of the gender of an organism. E.g. the male human has got one X- and one Y-chromosome, the female human two X-chromosomes. In contrast it is vice versa at the birds. The female bird has got one W- and one Z-chromosome, the male bird two Z-chromosomes.
- Autosomale heredity: The feature (or character), which is bequeathed, is not located on one of the two sex chromosomes.
- Sex-linked (also heterosomale) heredity: The feature (or character), which is bequeathed, is located on one of the two sex chromosomes (usually the larger of the two sex chromosomes is concerned, i.e. this one, which exists only once at the hen and twice at the cock).
- Dominant heredity: The dominant colour feature is visible. So it is not possible to bequeath it covered. One example for that is the green colour of the Lineolated Parakeet. If the green colour is fixed genetically, it is visible.
- Recessive heredity: The recessive colour feature usually is not visible. So it can be bequeathed covered. One example is the turquoise (or blue) colour of the Lineolated Parakeet. The green colour is predominant over the blue coloration. If one of the two homologous chromosomes own the non-mutated gene (wild colour), the other one a mutated (blue colour), the bird is green anyway, although he has got the potential for blue coloration. By this he can bequeath this feature to his offspring. Just if both homologous chromosomes carry the mutated gene, which is responsible for the blue colour of the plumage, the bird is actually blue. That bird then is homozygous for the colour "turquoise".
- Co-dominant heredity: None of the features is dominant or recessive, they complement each other. A famous example are the red and white peas of the geneticist Mendel. By crossbreeding a red blooming pea with a white blooming one he got pink plants, not red or white blooming plants (which would be the case in a dominant-recessive hereditary path). So, the characteristics of the blossom colour complemented each other.
It is the same with the dark factor (df). One example: A green bird has no dark factor. By mating this bird with another one, which possesses one dark factor (i.e. the information for a dark factor is located on one of the two homologous chromosomes), the offspring could have one or no dark factor, like their parents, because the green bird doesn't pass on any dark factor to his offspring. The bird with one dark factor can bequeath the information either "no df" or "one df".
The mating of two birds, each of it having one dark factor, could lead to birds with absolutely no dark factor, with just one dark factor or, al least, with two dark factors (double factor), because both birds pass on the information "no df" and "one df". By combining these four possibilities, new dark factor combinations may arise.
- Dark factor: As stated before, the dark factor is inherited co-dominantly. So, in all colour variations there are light, middle and dark birds. In the green and blue line, where the differences at the birds with or without dark factors can be measured best, exist separate notations:
green line: without df - green (wild colour); 1 df - dark green; 2 df - olive (green)
blue line: without df - turquoise; 1 df - cobalt (turquoise); 2 df - mauve (turquoise) or slate
In the ino-line usually one can't distinguish between birds with or without dark factors. So, these dark factors are only mentioned, if you can gather their existence from heredity, e.g. lutino with 1 df or creamino with 2 df.
- "Split-to-birds": These birds bequeath the colour features, which they don't show visibly. For example, a green bird can be split to blue. Please note, that sex-linked colour mutations like ino and cinnamon only can be bequeathed by male birds. This is because, as far as a female bird has got these characteristics, they are visible, due to the fact, that female birds only have got one Z-chromosome.
The indication of the split heredity is always given after the visible colour.
For example, the abbreviation for a male green bird, which is split to turquoise, is: