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PostPosted: Tue Jul 21, 2015 10:50 am 
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Deluxe Drake
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Gold pigments, their genes and their interactions.

This is where I admit to a slight oversimplification earlier. I said there are two colour pigments on chickens; gold and black. This is true, but whilst there appears to be only one gene affecting black expression, there are two genes controlling gold expression. They are Sex Linked Gold (s+) and Autosomal Red (Ar+). They are found on different parts of the bird, and which part varies depending on which E base the bird is built on. They are removed by different genes, and they interact with each other. In order to try to explain them in a semi-sensible fashion, I'm going to tackle the basics of gold in a four-part series. 'Knowing Which Gold is Which', 'Sex Linked Gold', 'Autosomal Red', and 'Interactions'.

I am going to step through the points one at a time, so bear with me game bird breeders! :)

Part 1: Knowing Which Gold is Which.

In order to understand the layout of Sex Linked Gold versus Autosomal Red on a bird, we need to revisit our colour bases. Generally speaking, most of the gold on a bird is Sex Linked Gold. On the cocks Autosomal Red appears on the shoulder, and on hens it may appear on the breast, on the body or not at all. So lets take a look.


Cocks

As previously discussed, the base colouration in cocks is very similar, and their gold layout is also very similar.

Extended Black 'E' and Birchen 'ER'

Here both birds have Autosomal Red 'Ar+' on their shoulder, which can be bright red, a more subdued orange, or even look gold, depending on other modifying genes. However this patch is always controlled by Autosomal Red. Both birds have Sex Linked Gold 's+' controlling their hackle and saddle, and it also controls the colour of the lacing on the Birchen cock's breast.

Note that both birds have black flight feathers on their wings, they are 'crow winged'. This is a handy way of knowing that your bird might be built on an E or ER base.

ImageImage


Wild Type 'e+, Wheaten 'eWh', Brown 'eb'

These cocks tend to be a bit showier with their gold than the previous two, but the principles are the same. The shoulder is Autosomal Red 'Ar+', the hackle, saddle and wing flights are Sex Linked Gold 's+'. Note that all three have gold wing flights, they are 'duck winged'. The only appreciable difference between the three is that the Wheaten cock (middle image) should not have any black shafting in his hacle, the other two often will, particularly the Brown cock (right).

ImageImageImage


Hens

Here's where things get a bit more changable.


Extended Black 'E' and Birchen 'ER'

These two are interesting in that there is no appreciable expression of Autosomal Red on them at all. All of their gold colouring is due to Sex Linked Gold.

ImageImage


Wild Type 'e+

The classic Red Jungle Fowl colouring. On these birds the gold hackle and gold part of the brown body colour is caused by Sex Linked Gold. The 'salmon breast' is caused by Autosomal Red.

Image


Wheaten 'eWh'

Wheatens are pretty easy to remember. The hackle is Sex Linked Gold, everything else is Autosomal Red. The 'salmon breast' has essentially spread over the entire body, accompanied by a reduction in black pigment, to give the characteristic 'wheat' colouring.

Image


Brown 'eb'

Ignore the pencilling, it's impossible to find a picture of a 'plain' brown hen. This colour is particularly favoured for patterning because again, there is no area of Autosomal Red on the bird; both the hackle and body are coloured by Sex Linked Gold.

Image

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PostPosted: Sat Aug 15, 2015 6:37 pm 
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Deluxe Drake
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Location: Canberra
Sex Linked Gold and Sex Linked Silver

This is the gene controlling the majority of the gold colouring on our birds. There are two alleles, Sex Linked Gold 's+' and Sex Linked Silver 'S', usually just referred to as Gold and Silver. As the shorthand suggests, Silver 'S' is generally considered to be dominant to Gold 's+', however like most things it's not actually that simple. Silver is the gene that turns gold parts of the bird white.

As the name itself suggests, this is a Sex-Linked gene, like Cuckoo which we talked about earlier. This means that it occurs on the larger sex-determining chromosome 'Z', which the hen has one of and the cock has two (opposite system to mammals). The smaller sex chromosome 'W' does not carry this gene. So the following gene combinations can occur.

Hen: s+/- Gold, S/- Silver
Cock: s+/s+ Gold, S/s+ Yellow and S/S Silver.

How the heterozygous state 'yellow' expresses appears to be quite variable depending on the base.

At it's most basic Silver is an allele that can be used to dramatic effect. For example it turns the Gold Laced Wyandotte into a Silver Laced Wyandotte:
ImageImage

It turns your Buff Columbian into a Silver Columbian:
ImageImage

And it turns your Gold Birchen into a Silver Birchen (hen on the left vs hen in the middle):
Image

It will turn a Wheaten hen into a Silver Wheaten hen. Note that both have the wheat body, caused by Autosomal Red.
Image
Image

The Silver gene will also turn our Wild Type or Gold Duckwing hen into a Silver Duckwing. Note that the breast, controlled by Autosomal Red, is still salmon!
ImageImage

Now, remember that cocks carry two copies of the gene. So we can have a Gold Duckwing s+/s+, a Yellow Duckwing S/s+ and a Silver Duckwing (pullet breeding) S/S:
ImageImageImage

Note that the Silver Duckwing isn't quite pure white on his hackle and saddle, and he still has a red shoulder. This is due to Autosomal Red. In order to get a showable Silver Duckwing, you need to also remove Autosomal Red. More about that in the next chapter! However, note that his shoulder is not as red as the those of the other two birds, this is because Sex-Linked Gold and Autosomal Red interact. More on that in the chapter afterwards.

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Last edited by shairlyn on Tue Jul 25, 2017 7:08 pm, edited 3 times in total.

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PostPosted: Thu Jan 14, 2016 7:08 pm 
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Deluxe Drake
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Location: Canberra
Autosomal Red Ar+

Lets talk about the second gold/red gene, Autosomal Red. As the name suggests this gene occurs on the Autosomes. An Autosome is any chromosome that is not a sex chromosome, and all that means is that ever bird has two copies. This is different to Sex Linked Gold where the rooster has two and the hen only one.

Autosomal Red is dominant. If your bird has one copy of the gene they will express it; the same if they have two. Only when they have both copies of the recessive 'ar' which does not encode the red pigment, will they lack Autosomal Red. As indicated by the plus sign, Autosomal Red occurs in the Red Jungle Fowl, and indeed in most of our domestic breeds. Birds that lack it are relatively rare, but we'll look at a couple.

We looked earlier at our Silver Duckwing birds (e+), and the handsome silver cock with the red shoulder. He still retains the red shoulder because he is S/S Ar+/Ar+ and still possesses Autosomal Red. To be completely silver and black, he needs to lack Autosomal Red and be S/S ar/ar. Compare these two birds; the first has Autosomal Red, the second doesn't.
ImageImage

You can clearly see the lack of the red shoulder in the second bird. He is a show bird and a 'cock breeder'. Ironically in game birds, the silver rooster is shown with a silver shoulder and so lacking Autosomal Red, but the silver hen is show with a salmon breast, and so retaining Autosomal Red. This means that you need to keep Cock Breeding (without Autosomal Red) and Pullet Breeding (with Autosomal Red) lines.

Here's a great picture that demonstrates the difference. Both the hens here are Silver S/-. The hen on the right has Autosomal Red and could be shown. The hen in the front lacks Autosomal Red and has a white breast. She is a cock-breeding hen.
Image

In Wheaten (eWh) birds we can look at the effects of a lack of Autosomal Red, whilst the Sex Linkied Gold is still present. The hen in front is a 'cream wheaten'; she has Sex Linked Gold but lacks Autosomal Red. The hens behind her have both Sex Linked Gold and Autosomal Red.
Image

Note that the cream wheaten hen's hackle is not as dark as that of the other hens; that is because Sex Linked Gold and Autosomal Red do interact and reinforce each other. Interestingly, a wheaten hen that had both Sex Linked Silver and a lack of Autosomal Red would be almost white!

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PostPosted: Sun Mar 19, 2017 4:20 pm 
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Deluxe Drake
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Location: Canberra
Red Leakage, Gold Leakage and Sun Discolouration

You have a bird with a pattern that is supposed to be a striking mix of black (or blue or lavender) and white, or maybe all white. But they're not. They have smuts and smears of yellow, orange or red on their feathers. You've given them a bath, and it's still there, right in the structure of the feathers. What's going on?

The discolouration could be due to one of three things:
* Red leakage from Autosomal Red
* Gold leakage from Sex Linked Gold
* Sun discolouration from spending lots of time outside.

How do we tell the difference and what can we do about it?

Red Leakage

Theoretically this occurs in birds who have Autosomal Red (Ar+) and are based on e+, eWh, and to a lesser extent eb. (I know I said that Ar+ doesn't express in eb, but it can have some effect from what I've read). It bleeds through as a red colouring.

On the left is a gorgeous silver-laced Wyandotte with pristine white centers to her feathers. On the right is a blue-laced silver wyandotte with red leakage.
ImageImage

Now I don't know what e base Wyandottes are normally built on, but the bird on the right either has too many copies of Autosomal Red, or isn't homozygous for E or ER, if she's supposed to be. I'll leave that one up to people who know the breed. I'd breed her to a good black-laced silver cock to correct it.

Red leakage is relatively rare, and can make some striking patterns in itself.


Gold Leakage

Image

Here's a lovely example of gold leakage. This bird is a cuckoo and should have bands of dark grey and white, but has a yellow colour leaking. Why? And what do we do about it?

In this case it's not because he's supposed to have Silver rather than Gold. Remember that Silver/Gold is sex-linked, so a male can have one copy of each, which makes him yellow, and would express across the whole bird. Cuckoos are not usually Silver, because they don't need to be. We find the answer if we consider what this lad would look like if he didn't have the cuckoo patterning, and the answer is probably something like this:

Image

This black fellow has yellow feathers peaking through his colour, which suggests that he has insufficient melanisers. So in order to clear up the gold out of the original cuckoo you need more melanisers to make the base colour completely black. Only when you have a solid base colour can you make a good cuckoo on it. Breed him to a nice, solid black girl to correct.

Of course, the leaky black fellow above could also be a Furnace/Furness, which is a melanised wheaten, and they're supposed to look like that. Which brings us back to using the correct e base. If you want nice, clean black and white birds, build on E or ER as a base, it's easier.

Sun Discolouration

This is exactly what it sounds like, and it's not genetic. Birds with white in their feathers will acquire a yellowish tinge if allowed to spend a lot of time in the sun. This happens particularly to the hackle and saddle of the males, and looks like this:

Image

Check out that lovely gold colour on the cock. Note that the hen is still a clean white. Here's a blue cuckoo set:

Image

The only solution for this is to wait until the birds moult and then keep them out of the sun until it's time to show them.

I'm sure you've noticed that Gold Leakage and Sun Discolouration look very similar, as both tend to affect the hackle and saddle, particularly in males. If you've raised the bird then if it was clean when young and turned yellow later, it's the sun. If it was always yellow, it's gold leakage.

If you've just bought the bird, then unfortunately you'll have to wait until it moults to find out.

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PostPosted: Sun Mar 19, 2017 5:24 pm 
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Showy Hen
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Good day Shairlyn s and welcome back .

thanks you for taking a time and explaining this genetic trait to us .

really appreciated .

all the best


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