Hi redrooster99,
A locus is the canvas on which the color of the bird's plumage is painted. They are called the "e locus". There are a bunch of them. eWh , eb, ER, EE and a bunch more. Each different e locus has different ways in which the colors react when they are painted on them. Take these two breeds. Columbian Wyandotte and Light Sussex. Both breeds use the color gene S ( the Silver gene). They also have a gene called the Co (Columbian) gene which
resorts (modifies) the dark color over the bird's body. This gene pushes dark coloring ( in this case, Black) to the outskirts of the bird's body, leaving the body itself, white. The dark coloring only appears on the neck, tail and parts of the wing feathers. ( But usually, you can't see the black on the wing feathers when the bird has the wing folded up against its side.
Ok, so we have a bird carrying a Silver gene and the Columbian color modifying gene. The bird looks like a white bird with a black neck and black tail.
But "looks" ,and genetics which cause them, can be 2 different things. The birds can look alike, but the colors will perform differently when you mate them.
Why?
In this case, it is because the two breeds, Columbian Wyandotte and Light Sussex are "painted" on 2 different "locus" canvases. The Columbian Wyandotte is painted on the eb locus. ( eb/eb S/S Co/Co ). The Light Sussex is painted on the eWh locus. (eWh/eWh S/S Co/Co) . The 2 locus's cause
colors and
gene modifiers perform differently in a breeding program even tho the 2 birds "look" alike.
( side note here. Birds have 2 kinds of feathers. The top feathers which we see when we look at them. The "underfluff" which is shorter and helps keep the bird comfortable. in all kinds of weather.)
The differences are:
eb locus:
1. the underfluff on these birds is colored. Usually a grey or slate color. It can vary in depth of color and whether it is on the
top end or
bottom end of each feather of the underfluff.
2. The
depth of color and
placement of the color on the underfluff affects whether black stippling (specks) will appear on
white parts of the birds body. So the breeder needs to balance the right
amount of color and the
right arrangement of color in the underfluff feathers so the birds body will remain pure white in its white areas.
the eWh locus:
1. This bird is also carrying the Silver gene and the color rearranging Columbian gene. It has pure white underfluff
all the way to the skin. The underfluff needn't
ever be colored. Because it is eWh based, this bird
doesn't need any color balancing in the underfluff in order to keep the white body parts pure white. Now it
is possible for black stippling to show up in the white parts of an eWh based bird like this. But it is because the breeder bred
too much black color into the black parts and it "leaked" thru into the white parts...
not because the breeder misbalanced any
hue in the underfluff.
N
ow you can see why it is important that folks understand the Light Sussex is eWh based. It makes a big difference in understanding the genetics which create the color...and in breeding the color correctly in future generations.
Best,
Karen
Waterford english Light Sussex
in western PA, USA
Footnote: Here is a URL to a list of genetic formulas for common poultry breeds: http://tinyurl.com/mlhleot .
Scroll down to the list in Post #6. It is the more updated of the two lists on that page.
The Chicken Calculator they mention is Kippenjungle that the other posters here have been using to teach you.
I know the formulas look complicated, but really they are just a string of locus names, gene names,
and gene modifier names strung out in a line. Once you learn how they perform, you can understand what the
bird looks like by reading the formula.