I wrote this commentary as one component of my May newsletter, which was sent to my mailing list yesterday. I’m posting it here as well so people who are searching for information on Coloured Sheep: A Colour Genetics Primer by Irina Böhme and Saskia Dittgen will be able to find it more easily.
Spring and early summer are such busy times in the fiber and shepherding world. I don’t know about you, but my Twitter feed is full of videos of lambs. Some people have trouble with Twitter and Facebook. I think they just aren’t following the right accounts, the ones with new critters discovering (1) standing up, followed by (2) bouncing.
It’s also shearing time. I’ve also been watching photos being posted of newly shorn fleeces, at their most delicious.
I listen in on discussions about genetics, especially among shepherds whose breeds either have complex color potential or who are working to tease out hidden color and pattern genes in any breed that is thought of as white-only.
I love, and have thoroughly read, Margaret Howard’s The Coat of Many Colors: A Survey of Sheep Color Pattern Expression and I Am a Shepherd, with their wealth of sheep-related genetic information, and have dipped into A. G. Searle’s Comparative Genetics of Coat Colour in Mammals (1968, so we’ve figured out a lot since, but nonetheless intriguing).
Now I am playing with a new book by Irina Böhme and Saskia Dittgen: Coloured Sheep: A Primer on Sheep Colour Genetics (Grossharthau, Germany: Irina Böhme, 2019. ISBN 978-3-9820761-0-2; readily available now through online searches).
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What fun!
The book presents the core principles of sheep color genetics in a playful way without oversimplifying the extremely complex topic. It does so by presenting three core concepts—base color, pattern, and spotting—and turning them into a card game. Each lamb receives one “card” for each of the three core elements—base color, pattern, and spotting—from each of its parents, and by setting out “hands” and looking at how they’re “played,” the book teaches its readers how to understand and begin to predict genetic outcomes relating to color.
While I’m going to show a little of how they go about that, my examples only hint at the clear explanations in the book. If you are at all intrigued, make yourself a gift of this new title.
Why there are so many white sheep
When we were working on The Fleece and Fiber Sourcebook, Carol Ekarius—the livestock person on the team (in contrast to my fiber background)—repeated often enough that I’ll never forget it that there can be color hiding in any breed, no matter how predominantly white its population seems. While I understood and accepted this, Coloured Sheep drilled home exactly how this can be the case.
The reason we don’t perceive any color in many breeds, for generations upon generations, is that WHITE patterning obscures everything else in an animal’s genetic make-up.
As long as at least one parent “plays” a card for white, the offspring will be white.
Figuring out the hidden genes
There’s something called progeny testing in genetics whereby the offspring provide clues to the hidden genetic makeup of the parents. A lot of breeding decisions for color involve figuring out what genes are hidden and bringing them into the open. The card game in this book sets up examples for doing that.
Here’s a situation where a colored ram and a white ewe produce a white lamb. The ram’s genetics are known. The ewe’s are not. The lamb doesn’t offer any new information.
When a colored lamb comes along in a flock of white animals, that means that both parents had genes that result in color and both passed one or more relevant parts of their genetics to the lamb. In the next example, the same ram and ewe have a gray lamb. This fills in three of the hidden pieces of the ewe’s genetics! She’s white, but she has more color to offer.
The cards for playing this game have been printed on the back pages of the book. They can be cut out and used as is, or there is a download file on the book’s website for people who don’t want to damage their books. (My cards in the photos are not quite typical. I used the PDF file and some manipulation with Photoshop and InDesign to adjust the card spacing slightly, then printed on yellow cardstock with my black-and-white printer. Color printing would have been prettier, but I don’t have that capacity at home.)
More than color is involved in genetics . . . but color is a LOT
Color is only one piece of sheep genetics, but it’s arguably the most enticing aspect. It’s plenty complex, with far more options than the book presents. Here’s a quote that gives some idea of the scope of color genetics (about all domesticated animals, not just sheep):
“Although to date more than 300 genetic loci and more than 150 coat-colour-associated genes have been discovered, which influence pigmentation in various ways, the genetic pathways influencing coat colouration are still only poorly described.”
Cieslak, Michael, Monika Reissmann, Michael Hofreiter, and Arne Ludwig. “Colours of Domestication.” Biological Reviews of the Cambridge Philosophical Society 86, no. 4 (2011): p. 885.
As multifaceted and full of unknowns as color genetics is, Coloured Sheep will give you a sold grounding in how the interplay works.
Can you tell I love this book?
My husband has A-positive blood, and I’m O-negative, so our kiddos helped him figure out his genotype: the kids are A-negative, A-positive, O-positive, and A-negative. So Mark’s genotype is AO+-. This stuff is so cool. :). I’m a recessive test-cross.