Icelandic Sheep: Colors, Patterns and Genetics.. planning for results

We now know that every sheep pulls its exterior appearance from 3 sets of genes inherited from each parent: 6 genes.

Black is dominant over Moorit... and the pattern Solid is recessive. So based solely on the appearance of the black lamb we can conclusively say that it carries: 1 black gene and 2 solid genes. We can also say that it carries the gene "no spotting" since spotting is recessive and requires two spotting genes to express. Without knowing about its breeding, we can't guess if it carries moorit, or if it carries spotting.

Our Moorit lamb, on the other hand, definitely carries 2 recessive moorit genes and 2 recessive solid genes. Again, we can't speak to the spotting gene without knowing the sheep's pedigree.

Without knowing the ancestry of these sheep, we decide to breed them. We get twins. One twin is black, one twin is moorit. Both are, of course, solid, but one twin shows spotting. Now we can say conclusively that both parents carry moorit, both parents carry spotting. We can say conclusively of our new black lamb that she carries moorit, and may carry spotting (remember, if both parents carried the gene for no spotting, she may not have the gene for spotting). About her solid moorit brother with spotting we can say with absolute certainty he carries 2 moorit genes, 2 solid genes, and 2 spotting genes. He is, in short, absolutely reliable genetically. If he's bred to a sheep with any other pattern, that pattern will express itself (solid is recessive). If he is bred to a black sheep, the offspring will be black. And if he is bred to a sheep carrying spotting, there is a 50/50 chance his offspring will be spotted.

What does our little white lamb hide under those lovely ringlets? Since she carries a pattern gene from each parent, and white is dominant, she hides a pattern in there. She may carry two white pattern genes... in which case she will always have white lambs no matter what she's bred to. She also carries two color genes, and she may, or may not, carry spotting.

We breed our white lamb to our black ram above and she has twins, one white and one black. About the white lamb we can say with certainty that he carries the color black, and the patterns white and solid. About the black lamb we can say with certainty that he carries the color black, and the pattern solid.

If we breed our white lamb again next year to the solid moorit ram lamb we created above what can we say if one of her lambs is moorit? Well.. we know she carries moorit. We can also say of her previous offspring that they carry moorit as well.

Suppose, however, she had a Grey Moorit lamb. Now we know she carries the patterns white and grey, since grey would be dominant over solid. Her lamb, who is a grey moorit will carry the genes grey and solid... and two moorit.

Which means that if we bred her, our Grey Moorit back to her father, we have a 50/50 chance of producing either another Grey Moorit, or a Solid Moorit. If we bred her to the black ram, we would have a 50/50 chance of showing either the pattern Grey, or the pattern Solid, but a 100% chance of showing black.

Suppose we bred our white lamb to our solid black ram and got... a black badgerface. Again, we won't know for certain if either our black ram or our white ewe is carrying moorit, but we do now know our white lamb carries badgerface as her second pattern.

And the same would hold true is we got a Black Mouflon.

Farms looking for specific colors and patterns can either use pedigrees to hazard a best guess at what their lamb is likely to be carrying... or buy proven sheep whose offspring give some clue as to the genes they're carrying. Part of the fun of Icelandic Sheep is the "surprise packages" every spring.

Let's see if you can predict the outcome of a few breedings:

You have a Moorit Mouflon ewe carrying spotting. You breed her to a White Ram you know carries black, grey, and spotting. What might you see come spring?

Well... the pattern White is dominant over Mouflon, effectively covering color. So you could simply have a white lamb carrying mouflon (or possibly another pattern). You could also find yourself with a co-expressed Black Grey Mouflon. If the ram is carrying moorit you could also find yourself with a moorit in a co-expressed Grey Mouflon. In short..  your lambs could be anywhere from snowy white to chocolate topped to black topped, with spotting or without!

No wonder my new shepherd was overwhelmed! 

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