Quote:
Hold on---getting an answer worked up.
OK...
Chicken plumage contains only two pigments: eumelanin (black) and pheomelanin (red). St the cellular level, these colours work a bit differently.
These pigments can be diluted or enhanced, moved to specific parts of the feather or specific parts of the birds body.
There are a number of genes that control plumage colour and pattern. They all work together to create the colour and pattern of any individual bird. Each gene has two or more alleles, or alternatives, that a bird can carry for that gene. Thus every bird has every gene, but what differs is the specific set of alleles the bird carries.
In general, a bird carries two copies of every gene (one copy on each chromosome), but the alleles may or may not be the same for a particular gene. When they are the same, the bird is said to be homozygous. When they are not the same, the bird is heterozygous. This statement relates to individual genes. Thus a bird can be homozygous for some genes and heterozygous for others. When a bird is homozygous (sometimes abbreviated hom), that variation of the gene is the only on present in the bird, and it will display and interact with other genes. There is no alternative form of the gene present to alter the genes action. However, when a bird is heterozygous (het) for a gene, how that gene pair interacts with other genes is determined by the dominance of the two alleles. Dominance is between two alleles of the same gene; it has no bearing on the interaction between separate genes.
A dominant allele expresses, even if only one copy is present; it suppresses the effects of other allele.
A recessive allele cannot express when a more dominant allele is present. (However, for some genes recessive alleles are leaky, and will give some indication of their presencea mottled bird might show the barest bits of mottling, a white bird may occasionally grow a non-white feather or two).
Incompletely dominant means that there is an intermediate result between homozygous dominant allele and homozygous recessive allele. Blue is an example of an incompletely dominant gene: Splash is homozygous dominant, not-blue (undlluted black pigment) is homozygous recessive. Blue is the heterozygous phenotype. Another classic example is a pink sweet pea from a red parent and a white parent.
Co-dominant means that both alleles express. The sweet pea mentioned above would have equal amounts of both red and white.
As stated earlier, the genes all interact. So in a bird who is wheaten and blue, the blue gene dilutes the black pigment that is present in the bird. It does not create a completely blue bird, but rather dilutes only the black. Likewise a partridge with blue becomes a blue partridge, or a birchen with blue becomes a silver blue (hobby names can be unpredictable).
I erred when I said co-dominant (I will say, though, that I said may be close to co-dominance) as co-dominance relates to the interaction between alleles of the same gene. I do not know of a term that incorporates this concept into separate genes. Epistatic and hypostatic are the inter-gene terms that more or less correlate to dominant and recessive; its not an exact correlation, though.
Let me say that I do not have a good working knowledge of how the blue and lavender genes work at the cellular level; if I did, I might better be able to explain why they work together as they do. Maybe Henk or David or Tim can better explain.
My intention was to say that both the characteristics of the blue gene (darker head, hackles and saddle (on males) and the characteristics of the lavender gene (strong and even dilution of all pigment) express in a bird who is blue (Bl/bl+) and lavender (lav/lav). The amount of difference between the head & hackles versus the remainder of the plumage is likely to be less than in a bird who is not also lavender. For some reason, the birds who are both seem to be slightly darker than those who are only lavender.
Likewise with splash, a bird who is Bl/Bl and also lavender (lav/lav) will display characteristics of both phenotypes.
Hold on---getting an answer worked up.
OK...
Chicken plumage contains only two pigments: eumelanin (black) and pheomelanin (red). St the cellular level, these colours work a bit differently.
These pigments can be diluted or enhanced, moved to specific parts of the feather or specific parts of the birds body.
There are a number of genes that control plumage colour and pattern. They all work together to create the colour and pattern of any individual bird. Each gene has two or more alleles, or alternatives, that a bird can carry for that gene. Thus every bird has every gene, but what differs is the specific set of alleles the bird carries.
In general, a bird carries two copies of every gene (one copy on each chromosome), but the alleles may or may not be the same for a particular gene. When they are the same, the bird is said to be homozygous. When they are not the same, the bird is heterozygous. This statement relates to individual genes. Thus a bird can be homozygous for some genes and heterozygous for others. When a bird is homozygous (sometimes abbreviated hom), that variation of the gene is the only on present in the bird, and it will display and interact with other genes. There is no alternative form of the gene present to alter the genes action. However, when a bird is heterozygous (het) for a gene, how that gene pair interacts with other genes is determined by the dominance of the two alleles. Dominance is between two alleles of the same gene; it has no bearing on the interaction between separate genes.
A dominant allele expresses, even if only one copy is present; it suppresses the effects of other allele.
A recessive allele cannot express when a more dominant allele is present. (However, for some genes recessive alleles are leaky, and will give some indication of their presencea mottled bird might show the barest bits of mottling, a white bird may occasionally grow a non-white feather or two).
Incompletely dominant means that there is an intermediate result between homozygous dominant allele and homozygous recessive allele. Blue is an example of an incompletely dominant gene: Splash is homozygous dominant, not-blue (undlluted black pigment) is homozygous recessive. Blue is the heterozygous phenotype. Another classic example is a pink sweet pea from a red parent and a white parent.
Co-dominant means that both alleles express. The sweet pea mentioned above would have equal amounts of both red and white.
As stated earlier, the genes all interact. So in a bird who is wheaten and blue, the blue gene dilutes the black pigment that is present in the bird. It does not create a completely blue bird, but rather dilutes only the black. Likewise a partridge with blue becomes a blue partridge, or a birchen with blue becomes a silver blue (hobby names can be unpredictable).
I erred when I said co-dominant (I will say, though, that I said may be close to co-dominance) as co-dominance relates to the interaction between alleles of the same gene. I do not know of a term that incorporates this concept into separate genes. Epistatic and hypostatic are the inter-gene terms that more or less correlate to dominant and recessive; its not an exact correlation, though.
Let me say that I do not have a good working knowledge of how the blue and lavender genes work at the cellular level; if I did, I might better be able to explain why they work together as they do. Maybe Henk or David or Tim can better explain.
My intention was to say that both the characteristics of the blue gene (darker head, hackles and saddle (on males) and the characteristics of the lavender gene (strong and even dilution of all pigment) express in a bird who is blue (Bl/bl+) and lavender (lav/lav). The amount of difference between the head & hackles versus the remainder of the plumage is likely to be less than in a bird who is not also lavender. For some reason, the birds who are both seem to be slightly darker than those who are only lavender.
Likewise with splash, a bird who is Bl/Bl and also lavender (lav/lav) will display characteristics of both phenotypes.
