Goat color genetics are extremely complicated! There are some basic principles, but beyond that is the realm of the Laymen's Nightmare. (I will include some links for that realm at the end of the post, for those interested.)
Polled
First of all, although it's not a color, we're going to talk about polled genetics for just a moment. "Polled" means that a goat is naturally hornless (a highly sought-after trait, as you may be able to imagine!) However, issues spring up given that the polled gene has been linked to hermaphroditism in homozygous kids (this means they have characteristics of both males and females...obviously not very useful in a goat. :)). Let's look at some of my favorite things...Punnett squares!
In these cases, P denotes the dominant polled gene, and p means the recessive horned gene.
This Punnett Square is for the case of a heterozygous polled doe (i.e. one polled gene, one horned gene) bred to a horned buck (like in the case of our goat Dora). In this case, because the mom will pass a dominant horned gene to half of her kids, meaning half of them will be polled.
This Punnett square looks at the breeding of a homozygous polled buck (i.e. two polled genes) with a horned doe. In this case, all the kids will be polled. Why then, you may ask, don't we just always use polled bucks? Well, let's go to the next Punnett square.
In this case, a heterozygous polled buck and doe are bred together. 1/4 of the kids will be horned, and 1/2 the kids will be heterozygous polled. The remaining 1/4 of the kids will be homozygous polled. However, here's where the intersex link comes in. If the PP kid(s) are does, they will be intersex. However, if they're bucks, they can be used for breeding. So trying to get a PP buck is not without risk. (And that's without mentioning that it's quite difficult to figure out if a goat is Pp or PP...)
Blue EyesLet's talk about blue eyes for a moment! Like the polled gene, the gene for blue eyes is dominant, although unlike with the polled gene, there's no intersex link, so we can breed for homozygous blue eyed goats as much as we want. :)
This is a Punnett square for a heterozygous blue eyed goat bred with a brown-eyed goat. We had this for several years with our goat Misty. This results in 1/2 and 1/2 blue eyes vs. brown.
This one is for breeding a homozygous blue eyed goat (like our goat Cassie) with a brown-eyed goat. All these kids will be blue-eyed.
This is two heterozygous blue eyed goats, which produces 1/4 brown eyed goats, 1/4 homozygous blue (that's how we got Cassie...) and 1/2 heterozygous blue.
Okay, now let's talk about...
Color Patterns
The main color patterns in Nigerian dwarfs are buckskin, chamoisee, and black. There are others (i.e. swiss markings, cou markings like those seen in Alpines, chocolate, and gold). Those ones are more rare, so we're just going to talk about those for now.
It's not entirely known how buckskin and chamoisee interact, precisely. (Or at least not simply). Each goat has two genes for color patterns, one recessive (not showed on the goat), and one dominant (the one that goat has). Black is always recessive. Thus, the easiest way to find out what pattern is recessive in a goat is to breed it to a black goat. The goat will have two general patterns of kid, one "their" pattern, or the one that they display, and one that's recessive.
Other factors than base color do play a role in color genetics--a goat can be roaned (have solid color areas spotted with white, a pattern often seen in pygmy goats), be "broken" (have solid white spots), have moonspots (have solid spots of a different color on the base color), have a color variant (for instance, chocolate buckskins substitute chocolate for black in the pattern), or have a faded pattern (i.e. there can be light buckskin, white buckskin, dark buckskin, etc.). We also don't know a ton about how those genetics work.
If you want more information on those patterns, as well as pictures of patterns, check out these links:
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