Quick Genetics lesson today. In conversations online (and in person) I am quickly coming to the conclusion that either very few people took basic High school Biology, or if they did, they slept through the genetics section. I find genetics to be a fascinating concept. Todays explanation is on simple dominant vs simple recessive. A simple dominant gene can override the visual evidence of a recessive gene. A simple dominant gene, then only needs one copy to express (be visually evident) on the goat. A simple recessive needs a 2nd copy of the recessive gene to be expressed on the goat who possesses the gene. In genetic inheritance then it goes something like this: Simple Dominant: You are the owner of Horned/Disbudded Molly. Horns in goats are recessive (meaning they need two copies of the horned gene to be horned). You breed her to Fred who is disbudded (genetically horned). Her babies will all have horns. You decide you hate disbudding, and you dont like horns, either. You want polled babies next year and since Polled is a simple dominant, as far as current research can tell, so you must go looking for a buck who is Polled. You find Timmy who is Polled (so he has at least one Dominant Polled gene) and breed Molly to Timmy. Molly/Timmy babies have a 50% statistical chance of being polled. Goats dont take math in high school, so sometimes the genes roll out in the babies so you get all polled or all horned. But per the math, 1/2 of Molly/Timmy babies will be polled. You get a cute polled doeling and you name her Tilly. Homozygous Polled goats (homozygous = two copies of Polled gene & no horned genes) are so far as mythical as the proverbial unicorn, but...you find a homozygous Polled buck the next year. His name is Zeke. You breed Molly (homozygous for horns) and her heterozygous Polled daughter Tilly (heterozygous = one polled gene, one horned gene) to Zeke. Molly and her daughter Tilly will both have all polled babies. Mollys babies will each have one copy of Polled, and one copy of Horned. Tilly babies have a 50% chance of having only polled genes. Simple Recessive: Molly is brown. You know that brown colors in goats are usually Dominant. You also know that one of Mollys grandparents was black, so she has a slim chance of carrying a recessive black gene. You want to breed for black babies this year, so you go looking for a buck who can give you black babies. Bob down the road is a brown buck, but his dam was black, so he carries one copy of a black pattern, as a black goat only has black genes to give her babies. If you breed Molly to Bob, and Molly carries a black gene, you have a statistical 1 in 4 chance of getting a brown baby. If Molly does not have a black gene, none of the babies will be black. You decide to keep looking as you want a better chance of getting a black kid. Someone else has George who is black. George only has black genes, so if your goat Molly has a black gene, then you have a 50% chance of getting black babies, and all of her babies will carry a black gene, so even if the kids are brown, you can keep one of them and breed them to another black goat to get a guaranteed 50% chance of black. If Molly has all brown genes, then the babies will all be brown, but all will carry black genes. You are in luck, and Molly has a gorgeous black doeling. You name her Sally. You decide you like black goats so much, you look for another black buck to breed Sally to. Fred is a handsome black buck and you breed Sally to him. Sally will have all black babies, because Sally and Fred only have black genes to give their kids.
Posted on: Wed, 23 Jul 2014 20:52:32 +0000
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