Hi, and welcome back to another in my series
of videos about the genetics of chickens. In my last genetics video, we talked about
gold-laced and silver-laced Wyandottes, perhaps more accurately described as black-laced gold
and black-laced silver. But as I hinted, not all lacing colour is
black. You’ve probably heard of blue-laced chickens.
And I bet you can guess how that blue lacing is made. It’s just like the blue feather
colour that we learned about in a previous video – the blue colour comes about because
the Bl gene is co-dominant with the bl (black) gene. If a chicken has only one copy of the
Bl gene, then she is blue, if she has no Bl gene, then she is black. And if she has two
copies of the Bl gene, then she is a colour called splash, which is almost white.
So, let’s apply this to the lacing colour of Wyandottes. And as we do that, remember
that the Bl gene only affects the expression of the black eumelanin pigment, the Bl gene
has no effect on the expression of the gold pheomelanin pigment.
Most Wyandottes have black lacing. And of course they have no Bl gene.
If we add one copy of the Bl gene, then hey presto the black lacing colour is going to
be diluted to blue. And what we have is a blue-laced Wyandotte – more accurately called
a blue-laced gold Wyandotte because the lacing colour is blue but the pheomelanin of the
gold ground feather colour is not affected by the Bl gene and is still gold.
Now if we happened to breed two blue-laced Wyandottes, half of their chicks would have
one Bl gene, inherited from either their mother or their father, and those would of course
be also blue-laced. A quarter of their chicks would by chance inherit the little bl gene
from mum and the little bl gene from dad, in other words they have no Blue gene, so
they are going to look black-laced, even though both their parents were blue-laced. As we
remember, the blue gene doesn’t breed true – the chicken must have one copy and only
one copy of the Blue gene in order for the colour to look blue.
And the other quarter of the chicks, who by chance inherit a Bl gene from each of their
parents and so have two Bl genes – what will they have? Since two copies of the Bl
gene make “splash”, they will have splash-coloured lacing. And since splash looks almost white,
these chicks will look like they have white lacing around the edge of each gold feather.
These chicks should be called “splash-laced gold”. They are very popular because they
are so unusual and rather pretty. And as you have guessed, they will breed true, just like
black-laced chickens, because the splash-laced chickens have two copies of the Bl gene, and
so will always pass on a Bl gene, so if you breed two splash-laced chickens together,
all their chicks will always be splash-laced too.
So just like before, one copy of the Blue gene makes the blue colour, two copies makes
splash, and no blue genes at all leaves the eumelanin unaffected and so black.
Now the splash looks kind of white, but it’s not really white, it’s really a very pale
blue-grey. And I think it looks kind of dirty, especially around the hackle. Most splash-laced
Wyandottes have quite blue-grey hackles. And I’d like the white to be pure white against
the gold ground feather colour – I’d like a gold feather outlined in pure white instead
of pure black. In fact, if you’ve looked at some of my videos, you might have spotted
a Wyandotte hen who looks like that – buff-gold ground colour outlined in pure white with
no trace of blue-grey around the hackle feathers. How is that possible?
Well, it needs a completely different genetic background, nothing to do with the Blue genes.
We need to introduce a gene called “Dominant white”
The symbol for the Dominant white gene is a capital “I”, which comes from the concept
that it Inhibits the black colour of eumelanin. It’s a relatively common gene, although
by all means not all chickens that look white have this gene. Of course you can guess that
it’s a dominant gene, just from its name, but it’s not completely dominant, and chickens
with two copies of the gene will be whiter than chickens with only one copy. Its main
effect is to inhibit the black eumelanin pigment but it does actually have a weak dilution
effect on pheomelanin as well as its stronger effect on eumelanin. It is not sex-linked.
So if we add this dominant white gene to our gold laced Wyandotte genotype, what will we
get? We keep the gene for the gold ground colour of each feather (which is written as
little s because it is recessive to the Silver gene that we already know about) and we keep
those three genes for making the lacing pattern, we don’t add any blue genes but we add dominant
white. The added dominant white gene tends to white out the black of the lacing. So we
get ta da, gold feathers outlined in white! Now we do have to say that there are a couple
of drawbacks. Firstly, one copy of the I gene isn’t totally
effective at whiting out the black completely, and an occasional black speck might show on
the white lacing. Secondly, remember that the I gene has a very
slight dilution effect on the expression of pheomelanin, so the gold ground colour is
diluted to buff. Unfortunately, if we have a chicken with two
copies of the I gene, the white lacing becomes less prone to black leakage but the buff ground
colour gets very washed out. All the same, I think dominant white makes
a very pretty buff-laced Wyandotte (which should really be called white-laced buff)
with none of that dirty grey smudging that you see in splash-laced chickens with a double
dose of Blue gene. I bred these buff-laced chickens using the
dominant white gene for several generations, including crossing them with gold laced and
silver laced wyandottes. I’ll share those experiences with you in my next genetics video.
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