The first gene to influence what an Icelandic sheep looks like is color. The sheep come in two colors: black and moorit (brown). White is not a color for these sheep, but rather a pattern. So even if you have a white sheep, it is in actuality a color that is "covered up" by the white. Black is dominant over moorit - therefore to be moorit, a sheep must inherit a gene for moorit from each of its parents.
PATTERN
There are five patterns of Icelandic sheep in North America (a sixth pattern gene, grey/mouflon exists in Iceland, but whether or not we have that pattern here is still being debated). The patterns in order of most dominant to most recessive are: white,grey,badgerface,mouflon and solid. (click on pattern to view)
Each sheep will inherit one gene for color and one gene for pattern from each of its parents. Therefore a sheep will have two genes for color and two for pattern (when that sheep is bred, it will contribute one of its color and one of its pattern genes to its offspring). The color and pattern genes have an order of dominance and recessiveness that influence how the sheep will look.
Because they inherit two pattern genes, and three of the patterns (grey, badgerface and mouflon) can be co-exhibited, you can have sheep that are (either black or moorit) grey badgerface,grey mouflon or even badgerface mouflon. (click on pattern to view)
SPOTTING
A third gene is one in which an animal will have - or not have - spots. To be spotted, the lamb must receive a spotting gene from each parent. If a lamb received only one gene for spotting, it will not be spotted, but rather it will "carry" spotting and could throw that spotting gene to its own lambs. The spots are so varied in how they can be exhibited that in Iceland they have actually named and classified 92 spotting patterns that include descriptions such as: dark eyerings; dark cheeks; Jacob's markings; hood and blaze; coat with blaze, stockings, etc. To view some examples of spotting patterns click here.
The easiest way to understand the way these genetics work is to start with a sheep that has the most recessive genes: a solid moorit. Add spots to that sheep and you will be able to know exactly what its underlying genetics for color and pattern are. The ewe at right is a solid moorit spotted ewe. Since solid and moorit are the most recessive of the genes, her genetic make up would look like this:
gene received from dam from sire
Base color Moorit Moorit
Base pattern Solid Solid
Spotting Gene Spot Spot
Since we know exactly what she will "throw" to her lambs, she is an excellent choice for bringing out hidden genetics (especially in breeding to white rams). And if we breed her to a spotted moorit ram, we know exactly what the lambs will be: spotted moorit.
White sheep are usually the hardest to figure out unless you know the entire history of their parents, or of the lambs they have produced. This white ram had a dam that was moorit spotted and a sire that was white. We don't know what the sire's underlying recessive genes were, so to plot out his genetics the boxes will not be completely filled out.
gene received from dam from sire
Base color Moorit Black
Base pattern Solid White
Spotting gene Spot ?
Because his dam was moorit spotted, we know that he carries spotting and moorit as recessives to throw to his own offspring. He threw a black lamb, so we know his color base is moorit/black.
When breeding a white sheep to a white sheep, there is some risk of producing lambs that are white/white for pattern. A homozygous white sheep will only have white to throw its offspring. And because white is the most dominant pattern, all of those lambs would be white (although they could throw other patterns depending upon the genetics of the other parent).
Another factor with white sheep is the possible exhibition of tan fibers, called phaeomelanin. Some sheep will have so much phaeomelanin that they look tan or almost a reddish color. Sprinkling of phaeo spots can make a white lamb look like a moorit spotted. The photo at right shows twin white lambs; one is brilliant white and the other has quite a bit of phaeomelanin.
A Black Sheep
Black sheep can be either homozygous for black or heterozygous carrying black/moorit color genes.
This black ewe's genetic make-up looks like this:
genes received from from dam from sire
Base Color Moorit Black
Base Pattern Solid Solid
Spotting Gene ? Spot
The reason we know she can "throw" moorit is because her mother is moorit - that was all she could throw - remember to be moorit, the sheep has to have two genes for moorit. It is possible to also have a black sheep that inherited two black genes and therefor its lambs would always be black, since the black gene will mask moorit that its lambs might receive from the other parent. This ewe can throw to her lambs the spotting gene she received from her sire. This black ewe, if bred to the white ram already discussed can throw lambs that are: white, black, moorit, black spotted or moorit spotted. If she had quadruplets, theoretically she could produce four completely different looking lambs.
Is that lamb BLACK or MOORIT?
Newborn lambs can be very dark in color and discerning between black and moorit can be difficult. A key place to look is the tissue surrounding the eyes. If the eye ring is black, the lamb is black; if the eye ring is brown, your lamb is moorit. However, lambs that co-express two patterns (i.e. grey & mouflon) may show a lot of phaeomelanin and this will make them look moorit, when they are still black! (Just to confuse things even more!!)
For information about registering Icelandic sheep with the Canadian Livestock Records Corporation, please visit this page: CLRC
grey spot on the ewe above.
