Chocolate Laced Blue?

[tadkerson]

Quote:
Genetics 202

In the chickens skin are special cells called melanocytes, these cells are where the pigments are made. The pigments are made and packaged in cell structures called melanosomes. A house is a cell and beach balls in the house are melanosomes. There are two kinds of melanosomes: eumelanosomes make and package black pigment (eumelanin) while pheomelanosomes make and package red pigment (pheomelanin).

Eumelanosomes have a well organized matrix (lots of framing like walls in a house) and are rod shaped in black areas of a bird; blue birds have eumelanosomes that are round.

Pheomelanosomes are not well organized and round.

The melanocytes have the ability to migrate. They move up to ( migrate from the dermis) and park next to a cell (in the skin) called a keratinocyte. The melanocytes then transfer the melanosomes to the keratinocytes. The keratinocytes then transfer the pigment to the growing feather.

A blue bird’s feathers contain a modified eumelanin (it has different chemical properties than black eumelanin) and the eumelanosomes are round. The eumelanosomes are loosely packed into the different parts of the feather- some parts do not contain eumelanosomes (hooks).

Black areas on birds contain eumelanin and the eumelanosomes are rod shaped. Eumelanosomes are tightly packed into the different parts of a feather.

Lavender birds have normal melanosomes. The melanocytes (pigment making cells) are normal. The lavender gene inhibits the transfer of the eumelanosomes and pheomelanosomes from the melanocyte to the keratinocyte. Normally the melanosomes travel from the center of the melanocyte to little fingers that stick out from the cell (dendrites). The keratinocytes then accept the pigments from the dendrites and place the pigments into the developing feather. Most of the pigment stays inside the melanocyte and does not make it to the feather follicle.


Dominant white- The dominant white gene interferes with how the eumelanosomes are produced (reduces the number of melanosomes made); causing them to be an irregular shape and to have an improper internal structure. The melanocyte does not recognize the eumelanosomes so the melanocyte destroys the eumelanosomes; they think the eumelanosomes are foreign and do not belong inside the cell.

I would hypothesize that the dun gene works similar to the dominant white gene. The mechanism does not work as well- some of the melanosomes are not recognized as foreign (pigments make it to the feather follicle) and others are recognized as foreign and are destroyed. This would produce a diluted color.


Tim

 

[nicalandia]

Quote:
Genetics 202

In the chickens skin are special cells called melanocytes, these cells are where the pigments are made. The pigments are made and packaged in cell structures called melanosomes. A house is a cell and beach balls in the house are melanosomes. There are two kinds of melanosomes: eumelanosomes make and package black pigment (eumelanin) while pheomelanosomes make and package red pigment (pheomelanin).

Eumelanosomes have a well organized matrix (lots of framing like walls in a house) and are rod shaped in black areas of a bird; blue birds have eumelanosomes that are round.

Pheomelanosomes are not well organized and round.

The melanocytes have the ability to migrate. They move up to ( migrate from the dermis) and park next to a cell (in the skin) called a keratinocyte. The melanocytes then transfer the melanosomes to the keratinocytes. The keratinocytes then transfer the pigment to the growing feather.

A blue bird’s feathers contain a modified eumelanin (it has different chemical properties than black eumelanin) and the eumelanosomes are round. The eumelanosomes are loosely packed into the different parts of the feather- some parts do not contain eumelanosomes (hooks).

Black areas on birds contain eumelanin and the eumelanosomes are rod shaped. Eumelanosomes are tightly packed into the different parts of a feather.

Lavender birds have normal melanosomes. The melanocytes (pigment making cells) are normal. The lavender gene inhibits the transfer of the eumelanosomes and pheomelanosomes from the melanocyte to the keratinocyte. Normally the melanosomes travel from the center of the melanocyte to little fingers that stick out from the cell (dendrites). The keratinocytes then accept the pigments from the dendrites and place the pigments into the developing feather. Most of the pigment stays inside the melanocyte and does not make it to the feather follicle.


Dominant white- The dominant white gene interferes with how the eumelanosomes are produced (reduces the number of melanosomes made); causing them to be an irregular shape and to have an improper internal structure. The melanocyte does not recognize the eumelanosomes so the melanocyte destroys the eumelanosomes; they think the eumelanosomes are foreign and do not belong inside the cell.

I would hypothesize that the dun gene works similar to the dominant white gene. The mechanism does not work as well- some of the melanosomes are not recognized as foreign (pigments make it to the feather follicle) and others are recognized as foreign and are destroyed. This would produce a diluted color.


Tim

thanks for you info Tim, you are a great teacher..

 

[Heather08]

Quote:
I have the same color hen and own no blues..

 

[Henk69]

Quote:
The first statement appears to be false. There are different eumelanins, but the shift from black to brown is not caused by altered chemical structure.

The brown eumelanin effect does not need pheomelanin, since bird species without pheomelanin (eg geese) also have brown color.

http://mail.sumnercomm.net/~rmangile/Pigeons/Biosynthesis of Eumelanin and Pheomelanin.html

 

[nicalandia]

Quote:
I have the same color hen and own no blues..

http://img.photobucket.com/albums/v649/Paxo28/150.jpg

sorry that hen does not look like the ones attack posted...

 

[nicalandia]

Quote:
The first statement appears to be false. There are different eumelanins, but the shift from black to brown is not caused by altered chemical structure.

The brown eumelanin effect does not need pheomelanin, since bird species without pheomelanin (eg geese) also have brown color.

http://mail.sumnercomm.net/~rmangile/Pigeons/Biosynthesis of Eumelanin and Pheomelanin.html

henk there most be something affecting how Dun looks, in some birds it looks nothing like chocolate and in others it looks chocolaty color..

example. this boy does not look very chocolaty

but this boy does...

could it be lack/pressence of melanizers? Phomelanin enhancers?

 

[tadkerson]

Quote:
The first statement appears to be false. There are different eumelanins, but the shift from black to brown is not caused by altered chemical structure.

The brown eumelanin effect does not need pheomelanin, since bird species without pheomelanin (eg geese) also have brown color.

http://mail.sumnercomm.net/~rmangile/Pigeons/Biosynthesis of Eumelanin and Pheomelanin.html

Henk,

I looked at the article and I can not get to the book to check the citation. I have copied some of the information below.

Genetics 303

Quote:
I would agree that the dun color could be due to the optical perception of color due to the physical properties of the eumelanosomes. This is a plausible explanation for the brown color due to the fact that the dominant white allele causes an irregular shape in the melanasomes and also effects the internal structure of the melanosomes. Both of these differences could effect color perception due to light absorption and reflection. The dun allele is similar to the dominant white allele because of its allelic relationship and therefore it may act in a similar manner.

There is also the possibility that the dun color is a mixture of red and black pigments. According to the research I have read tyrosine is the rate limiting factor for the production of eumelanin- low levels of tyrosine foster pheomelanin production. The cells could possibly be switching between the production of the two pigments based upon the levels of tyrosine and producing the heteropolymers or melanosomes containing both polymers ( pigments).

There are differences in the chemical properties of black eumelanin- the eumelanin that is found in blue birds is different that that found in black birds. There has to be some difference in the molecular structure for the properties to exist. I do not remember what the properties are- I can not remember what paper I read that contains the information. They may have to do with solubility and photo chemical properties- I just can not remember.

A simple test for the presence of sulphur can help eliminate all the guessing. Cysteine contains sulphur and reacts with dopaquinone to produce a precursor to pheomelanin. Eumelanin does not contain sulphur.

This test would tell us if the feathers contain pheomelanin. No pheomelainin and the brown color is due to the optical effects of the eumelanosomes or possibley the concentration of black pigment in the eumelanosomes

If the feathers contain pheomelainin, it still could be caused by some factor (tyrosine inhibition) limiting the production of eumelanin and favoring some pheomelanin production so that you get a mixture of the two pigments producing a brown color. Assuming the birds do not contain any genes that would cause the production of red pigments i.e. gold allele or autosomal red genes.

Tim

 

[tadkerson]

Quote:
The first statement appears to be false. There are different eumelanins, but the shift from black to brown is not caused by altered chemical structure.

The brown eumelanin effect does not need pheomelanin, since bird species without pheomelanin (eg geese) also have brown color.

http://mail.sumnercomm.net/~rmangile/Pigeons/Biosynthesis of Eumelanin and Pheomelanin.html

henk there most be something affecting how Dun looks, in some birds it looks nothing like chocolate and in others it looks chocolaty color..

example. this boy does not look very chocolaty
http://i1085.photobucket.com/albums/j437/nicalandia/chocboy.jpg
but this boy does...
http://i1085.photobucket.com/albums/j437/nicalandia/ChocRoo.jpg


could it be lack/pressence of melanizers? Phomelanin enhancers?

I have noticed the variable expression one would see in dun birds and have lots of questions. If I had several years and a university lab- I could answer the questions.


Tim

 

[nicalandia]

and here we have it...Chocolate Laced Mauve(just like Chocolate Laced Platinum Blue but with recessive choc not dun)

bird is from Grant Mauve project..http://www.orpingtonbantams.co.uk/choc.htm (scroll all the way down)