Day: October 29, 2011

Saturday, 29 October 2011

10:04 – Barbara continues to improve. She’s even taking Colin for short walks down the block and yesterday while I wasn’t looking she rolled the trash cart back down the driveway. She goes to the doctor next week for a follow-up visit, and I suspect he’ll approve her to drive again and return to work. She’s going stir-crazy here. Of course, Colin is going to be a problem because he’s now used to having her home all day every day.

Yesterday I finished up the group of lab sessions on microorganisms and started on a group of lab sessions on genetics. Right now, I’m working on a lab about Mendelian traits and inheritance. There are actually relatively few pure Mendelian traits in humans, but one of them is a classic. The ability to taste phenylthiocarbamide.

Fortunately, I also did a self-sanity check. Beginning biology students often make the false assumption that dominant and recessive Mendelian traits correlate to the percentages of individuals in a population that exhibit the dominant and recessive phenotypes. In other words, a high percentage of individuals exhibit the dominant phenotype and a much small percentage the recessive phenotype. A moment’s thought establishes that’s not the case, at least for anyone who’s aware that Huntington’s disease is a dominant Mendelian trait.

But I made that exact false assumption with regard to Colin and his prick ears, assuming that floppy ears in dogs are Mendelian dominant and prick ears recessive. In fact, floppy ears are a recessive Mendelian trait. The fact that probably only one in ten thousand Border Collies has prick ears doesn’t indicate that prick ears are recessive, but merely that Border Collie breeders have selectively bred a population of Border Collies that are almost entirely recessive with respect to ear conformation. (Not that they were selecting for ear type specifically, but sometimes something you don’t care about one way or the other is part of the package that you’re breeding for.)

Now the only problem is that I don’t remember either Colin’s mother or father having prick ears. Hmmm.

10:42 – Duncan was a giant among Border Collies, standing about 4″ (10 cm) taller than other large males and weighing half again as much despite the fact that there was no fat on him. When Duncan was two or three years old, we took him to a Carolina Border Collie Rescue event held at a farm owned by one of the volunteers. There was a large open field and a herd of about 100 Border Collies running around in it. We could pick out Duncan instantly because he towered above all of the other BCs, except one who was even larger than he was. (Despite the fact that Duncan was registered purebred, we always suspected that he might have some English Shepherd in his bloodlines.)

Barbara just got out a photo of Duncan standing on our front porch that showed the line of his back was at the line of mortar above the seventh row of bricks. She then took Colin out on the front porch while I stood back to see the level of his back relative to the bricks. At eight months old, Colin is already taller than Duncan was as an adult. He’s going to be a very big boy.

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