Cream Legbars

[GaryDean26]

Well...I guess I call it a gene mutation and they call it a retrovirus? A gene mutation can be either and deletion or insertion to DNA or RNA genome. It sounds like they are saying that the blue egg mutation that occurred several hundred years ago and then selectively breed for was the result a mutation in the form of an insertion to the RNA genome.

A retrovirus is a family of single strand parasites that insert their own genetic code into the RNA of a host cell (rather than the DNA like what we call a virus). This insertion of the the RNA obligates the host cell to reproduce the parasite rather than build new cells to sustain itself. If the blue egg were caused by a parasite, then the parasite would infect the host and once the host was destroyed it would have to move to new hosts. I can see the logic in theory that a retrovirus introduced a mutation into a chicken 300 years ago and after the host destroyed the retrovirus the damage to the RNA was not repaired changing the protein that was produced to something that cast the blue hue to the shell. I can not see the logic in a retrovirus living in lines of blue egg laying chickens for 300 years and breeders selectively breeding for birds that have the retrovirus, those that don't have the retrovirus, those that are split for the retrovirus, etc. That is not how it works. Retrovirus don't just target the part of the cells from dad who was the an Easter Egger, but no the part of the cells from mom that what laid white eggs. They attack any cell they are in their range of and destroy the host if the host can't destroy it first. They also don't create an occasional blue egg. A hen that lays a blue egg will lay every egg blue her whole life. Not nine brown eggs and then a blue egg followed by another nine brown egg. Saying that your Americana, Cream Legbar, or Auracana have a retrovirus sounds like science fiction at its best to me.

Just my thoughts and anyone who has read the Legbar Thread knows that my options don't always turn out to be right.

 

[racinchickins]

Should the cream legbar eggs I got from ebay be a sea green or a light blue? They are more green than blue, but in the right light there is a blue tint.

Both sets of eggs I got were definitely blue. Not like a Robin's egg, but nobody who saw them thought they were green.

 

[dretd]

I think this retrovirus article is pretty convoluted stretch of the truth. I am not buying it. They say a new study was done, but the information on the make up of the Blue eggs was studied in the 1930's. The 1930's study also included the inheritance of the blue egg and proved it was a dominant gene. I am going to be the first to say that this idea of "an occasional blue egg popping out" as a result of a "high concentration of a retrovirus" is totally ridiculous. The gene may work in a different manner from other genes, but it is not a retrovirus. I think BoingBoing.net is full of it.

Actually, the problem is that the original scientific article was mis-translated into layman-ese.

Here is a link to the original:
http://www.plosone.org/article/info:doi/10.1371/journal.pone.0071393

Here is a different article published from Chinese researchers:http://www.plosgenetics.org/article/info:doi/10.1371/journal.pgen.1003183

When there are two corroborating scientists that have come to the same conclusions independent of one another, it does add quite a bit of weight to the merits of the discovery.

The insertion event(s) in the South American Mapuche and Chinese Dongxiang 'blue' egg laying breeds may be independent of one another as they are not identical. I would skip over the technical parts and go straight to the discussion.

 

[dretd]

Well...I guess I call it a gene mutation and they call it a retrovirus? A gene mutation can be either and deletion or insertion to DNA or RNA genome. It sounds like they are saying that the blue egg mutation that occurred several hundred years ago and then selectively breed for was the result a mutation in the form of an insertion to the RNA genome.

A retrovirus is a family of single strand parasites that insert their own genetic code into the RNA of a host cell (rather than the DNA like what we call a virus). This insertion of the the RNA obligates the host cell to reproduce the parasite rather than build new cells to sustain itself. If the blue egg were caused by a parasite, then the parasite would infect the host and once the host was destroyed it would have to move to new hosts. I can see the logic in theory that a retrovirus introduced a mutation into a chicken 300 years ago and after the host destroyed the retrovirus the damage to the RNA was not repaired changing the protein that was produced to something that cast the blue hue to the shell. I can not see the logic in a retrovirus living in lines of blue egg laying chickens for 300 years and breeders selectively breeding for birds that have the retrovirus, those that don't have the retrovirus, those that are split for the retrovirus, etc. That is not how it works. Retrovirus don't just target the part of the cells from dad who was the an Easter Egger, but no the part of the cells from mom that what laid white eggs. They attack any cell they are in their range of and destroy the host if the host can't destroy it first. They also don't create an occasional blue egg. A hen that lays a blue egg will lay every egg blue her whole life. Not nine brown eggs and then a blue egg followed by another nine brown egg. Saying that your Americana, Cream Legbar, or Auracana have a retrovirus sounds like science fiction at its best to me.

Just my thoughts and anyone who has read the Legbar Thread knows that my options don't always turn out to be right.

You are on the right track. The retrovirus that is inserted into the host organism's cell does not overtake the cell and does not prevent it from replicating. That host cell will still divide (and the retrovirus will divide along with it) and live. The retrovirus will simply tell the cell that it needs to replicated the retrovirus as one of its activities. The cell will oblige, make some virus proteins, package them up and send them out to infect more cells. Some are more 'friendly' to the cell than others.

The retrovirus starts out as a strand of RNA and when it gets to the host cell, it uses an enzyme called reverse transcriptase to make DNA. That DNA is then inserted into the host's own DNA in the nucleus of the cell.

Most insertions are in 'regular' cells and wont be passed on to the children of the host. Occasionally, the insertion is in a germinal cell (the egg or sperm cells) and that will be passed on to that individual child and all cells of that child will carry the retrovirus. These retroviruses are then said to be endogenous. Depending on the part of the genome that the retrovirus is inserted into, there are various mutations that come about. This is the type of insertion that would be responsible for the 'blue egg' gene. The scientist can see exactly where the retrovirus is inserted and if two different animals have the same exact location for the retrovirus then it is evidence that they have the same source for the mutation. If the retrovirus is in a slightly different location, then two separate insertion events may have happened. The Chinese paper thought the origin was inconclusive and the English paper thought there were two separate events, if I remember right as the insertions were close but not identical between the Asian and South American birds.

Some researchers have speculated that the blue egg coloration protects the embryo from UV light so there may be an advantage for an egg to have this shell color at higher altitudes. The selective breeding would come in when a person thought they were pretty and wanted to breed more of the blue color, much like we have preferences today. Many folks want blue eggs and in fact like the blue color better than the green tint, while others think they are all pretty and aren't selecting only for blue. There are a few articles from South America on blue eggs I will try to round up and post.

Retroviruses are the viruses types that are responsible for the Human 'AIDS' virus and the Feline 'AIDS' virus as well as some forms of cancer. Some folks say they are obligate parasites, although they do not meet all of the criteria necessary to actually be alive.

Clear as mud, right? Its actually a very detailed area of cell biology and immunology.

 

[dretd]

Should the cream legbar eggs I got from ebay be a sea green or a light blue? They are more green than blue, but in the right light there is a blue tint.

I know many people prefer a blue color over a green. I have received egg shipments from several breeders and to my eye I would call them more on the green side, but others my think they are more blue.

I have been researching the origins of the 'blue' color from South American sources. I am hampered because my Spanish skills are not very good and washing the sources through google translate has its flaws as well. Some folks in South America are trying to formalize the blue egg laying breeds, but I fear some of the information has been derived from American and European sources thereby contaminating the originality of the information.

Here is a link to the breeders group: http://ln.fica.cl/muestra_noticia.php?id=653#.UjeLCD_iRCL
Now the photo on my Kindle Fire had the darker tinted eggs looking rather greenish and the lighter ones blue, but on my laptop they look more blue. I think my Kindle Fire color is actually more accurate. Here is the photo that accompanies the information:


Here is another source translated through google translate. I have bolded the statement regarding the egg color: http://mapuachawal.blogspot.com/
"Shape and color of the egg:
The color of the eggs from the hen is sacred to the Mapuche. Says one of the many myths about blue eggs "the Mapuche made a covenant with their gods, in which they pledged to take care of the chickens and, in exchange for those, the hens give eggs with the color of the sky, while the agreement is respected. " For this reason, the color of the eggs of the hen Mapuche must be based on blue pigments, namely Turquoise, Light Blue and Green. Eggs are preferred turquoise and blue over the green because the latter not only have the blue egg gene, but also have the coffee egg gene (brown or brown eggs are beyond our breed). The eggs are preferred deeper blue on blue paler because hybridity tends to pale blue. The shape of the egg is more well rounded as the eggs of wild chickens and eggs size is rather small, since large eggs came with laying hens selected generation after generation to lay larger eggs.

The blue color of the eggs in the hen Mapuche is based on race. The blue egg originated in Chile and is typical of the Hen of the Mapuche, although any other breed crosses by Mapuche can chicken blue eggs because the gene is easily transmitted and dominant character."

 

[ChicKat]

I agree that the statement is pretty misleading. "An occasional blue egg" would imply that the hen lays other colors...perhaps the writer meant occasionally this chicken will lay an egg...LOL.
Statement also implies that this chicken caught a retrovirus and that caused a blue egg. Could be 300-years ago the retrovirus caused the mutation ..... but then the whole process changed, the pigment comes from a different source, the pigment saturates the whole shell, so the coloration process is different. It's 'harder on the hen' to produce the blue pigment etc.

Perhaps started by a virus - but some significant changes as a result ---

Thanks for posting normanack, GaryDean26 and Dretd.

Bama1 Congrats on that egg!

ETA - lots later -- more stuff on the virus-causes-blue-eggs
https://www.backyardchickens.com/t/824009/blue-eggs-a-virus#post_12023303

and my latest and greatest -- although off topic entirely:
https://www.backyardchickens.com/t/825086/a-hen-lays-a-lavender-egg-i-want-one

 

[1muttsfan]

Nomenclature can sometimes be confusing. Retrovirises are not in the classic sense "alive" - they are more like little packages of genetic material that have the ability to manipulate genes by inserting themselves in. The word Virus automatically makes us think of a parasite, but they actually can be, like bacteria, either deleterious, neutral or even beneficial. Once they are inserted into the genome and those genes are replicated to produce offspring, they become a part of the genome and are no longer foreign material.

I agree that the condensation of the original article was very misleading - blue eggs "occasionally pop up" in Araucanas? Someone did not do their research.

 

[Brada Puhi]

Aloha kakou,

We do know that HPV - Human papilloma(?) Virus, causes damage to the DNA of a cell causing cancer.

In gene therapy, retroviruses are used to modify the DNA of a person similar to how Dretd was describing.

I didnʻt read the article, but these days they can look at the DNA and see how many letters(base pairs) makes up the difference. If it was a regular old mutation, then only a few letters would be different or rearranged.

A retrovirus, would make a longer change in the DNA. So I wonder how many letters are different.

Does anyone know?

aloha, Puhi

 

[GaryDean26]

I have been researching the origins of the 'blue' color from South American sources. I am hampered because my Spanish skills are not very good.

I have a 4 year degree in Spanish and have done some freelance traslations. I am already behind on my readling list but if you ever get stuck on transaltions I could look as some sections.

 

[write2caroline]

I had some really lovely cream leg bars. I recently lost them both to a predator but next spring I want to get some more. They were wonderful. The pullet was an excellent layer and she went broody for 60 days, I finally let her hatch chicks to make her stop. They didn't have a very big puff on head - their newer stock is more pronounced but they were really great!
Caroline