Icelandic Sheep: A Primer for Color Pattern Genetics
One of the things that makes
raising Icelandic sheep so very
interesting is the myriad colors
and patterns that they can come in
(add to that their spotting factor
and the possibilities are endless).
But the confusion over figuring
these pattern genetics out is one of
the hardest things for new
breeders so I am going to try to
simplify things as much as I can
here.
COLOR
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.
Putting it all together
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.
What about a white sheep?
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
What is that mysterious
grey spot on the ewe above.