Notes from the NorthBranchBreeding for those other traits
Alrighty then - we all know that outstanding dairy capabilities and exceptional fleeces are what we SHOULD be breeding for, but what about those just-for-fun traits that are considered optional... such as eye color or naturally polled? This is the next layer of genetics which includes dominant and recessive genes - a study which I would highly recommend delving into! This misunderstood phenomena has many folks assuming that since blue eyes and polled (to name two) make less frequent appearances in offspring than their counterparts (brown-eyed and horned), then it must follow that these traits are recessive when, in fact, both are dominant!
Another common misconception is that if a gene is dominant, it will always be expressed in the progeny, which also is not at all the case. Often a goat with blue eyes will throw brown eyed kids - this even happens when both parents are blue eyed! So how does this work then, and how do we go about increasing our chances of producing some of these "bonus" attributes in our Nigoras?
The easiest way to get a handle on breeding 101 is to break down the biology. The DNA of each animal species has a certain number of chromosomes arranged in pairs (goats have 30). These chromosome pairs enable genetic combinations that will determine which characteristics will be expressed in the offspring. A goat kid will inherit half of its genes (one of each of the 30 pairs) from its mother and the other half from its father.
Some of these genes are dominant (like blue eyes or polled) and some are recessive (like brown eyes and horns). If the offspring receives a dominant gene from each parent (let's say, for eye color), the result will be a kid with blue eyes. Likewise, if a kid receives recessive genes for eye color from both parents, it will have brown eyes. But if one parent donates a (dominant) gene for blue eyes, while the other parent donates the corresponding (recessive) gene for brown eyes, the dominant trait will be expressed - the kid will be blue eyed. There is no such thing as a goat who is a "carrier" for a dominant gene - if the goat kid has inherited a dominant gene, it WILL be expressed. So in simplest terms - a dominant trait is expressed if the goat has at least one copy of the gene, whereas a recessive trait is expressed only when two copies of the gene are present.
The explanation of dominant genes further diverges to include the terms "homozygous" (an animal possessing both copies of a dominant gene) and "heterozygous" (an animal who possesses one copy of the recessive gene, the expression of which is muted by the opposing dominant form of that gene).
So, if I have two blue-eyed goats, they can be either homozygous for the blue-eyed gene, or heterozygous. Since I am not a geneticist with the ability to dissect DNA at the microscopic level, I would assume both goats are heterozygous - that is, they each possess one copy of the blue-eyed gene and one copy of the brown-eyed gene. In science class, we always denoted the dominant gene with a capital letter and the recessive gene with its lower case companion, making each goat in our sample: Bb. (Remember, the dominant copy of the gene will mute the recessive copy of the gene for brown eyes, so a goat having the Bb genes will always present as blue-eyed).
Pairing two Bb goats will have three possible outcomes: there would be a 50% chance of the kids being Bb (or heterozygous for blue eyes - like their parents); the possibility for brown eyed kids (bb) would be 25%; and a 25% chance of producing a homozygous (BB) kid. A goat who is homozygous for blue eyes will ALWAYS produce blue eyed offspring and thus, would be the most desirable outcome for the breeder who wishes blue eyes to be a recurring theme in his herd, however, physically there is no way to differentiate them from their heterozygous Bb siblings (who still have the ability to produce progeny with brown eyes).
As a comparative example, a (Bb) blue-eyed goat who is paired with a (bb) brown eyed goat has a 50% chance of producing either blue eyed or brown eyed offspring. Of the blue eyed offspring, all of them would be Bb or heterozygous for the blue eyed trait and have the ability to produce brown eyed offspring. As I mentioned earlier, brown eyes and horns are both recessive in goats - two brown eyed goats will NEVER produce a blue eyed kid, and two horned goats will NEVER have a polled kid.
The fact is, I DO prefer blue eyed goats and will select for them, providing everything else about the goat passes my scrutiny. Because of my conviction to produce the best possible Nigoras, blue eyes will always be a choice that comes secondary to "all the right stuff," such as confirmation, F-gen, percentages, and the parent's propensity towards dairy capacity and/or outstanding fleece. If you feel the ability to choose for the whole package is beyond your skills, don't despair - believe me when I say we ALL feel this way! Genetics is a murky business known only to God, however, the longer you keep at it, you may begin to pick up things that help you to recognize which kids are likely to turn out the way you hope.
GOOD LUCK on your path to SUCCESS!!