Genetic Things

[Digit]

Interesting, in this list of human traits with simple inheritance patterns, I would have thought smooth chin was dominant and cleft chin recessive, since I rarely see people with cleft chins. I suppose that list is a gold mine of "what are you?" discussion.

Updated: I guess I misunderstood. I think "recessive" is the more common (the way they made the list), since "normal number of fingers" is in the recessive column. When I think dominant in terms of Mendelian genetics, I think of "if at least one of them is X, you get X trait" and recessive is "you need both to be X to get X trait."

[Zedability]

Interesting, in this list of human traits with simple inheritance patterns, I would have thought smooth chin was dominant and cleft chin recessive, since I rarely see people with cleft chins. I suppose that list is a gold mine of "what are you?" discussion.

Dominant/recessive doesn't necessarily correlate to frequency. If the majority of the population is recessive, than most people are going to procreate with other recessive people. For instance, you see a lot of blond hair and blue eyes in Scandinavian countries, even though those are recessive.

[Digit]

OK, so it is dominant = at least one, you get X and recessive = you need both to get X. Interesting that polydactyly is dominant.

[Digit]

Dwarfism is on the dominant side of that list, but I know I've seen dwarf parents (at least one of the parents) with normal-height kids. I guess there are different kinds of dwarfism, or that list isn't exactly right.

*D'oh. I always get it wrong. Of course a parent with a dominant trait would express it but could pass a recessive by chance to their child (assuming they're not homozygous). I've never seen two normal-height parents give birth to a child with dwarfism. The real inconsistency would be two recessive parents with a child with a dominant trait.

[Katya]

Dwarfism is on the dominant side of that list, but I know I've seen dwarf parents (at least one of the parents) with normal-height kids. I guess there are different kinds of dwarfism, or that list isn't exactly right.

People with achondroplasia (the most common kind of genetic dwarfism) are heterozygous dominant for the gene, which means that they have one gene for dwarfism (D) and one gene for average height (d). Since dwarfism is dominant, anyone with genotype Dd will be a little person. However, if two Dd parents have children, their children have a one in four chance of being genotype dd, which would make them average height. (They also have a one in four chance of conceiving a fetuses with genotype DD, but those fetuses are nonviable, which is how you know that any child or adult with dwarfism is Dd.)

Incidentally, average height parents can also have children with genetic dwarfism if there's a sporadic mutation in that gene when the child is conceived.

[Digit]

I should have said "little person" instead of "dwarf" as the noun form of a person with that condition, according to mainstream sensitivities, shouldn't I?

[Katya]

I should have said "little person" instead of "dwarf" as the noun form of a person with that condition, according to mainstream sensitivities, shouldn't I?

I believe so. I have a friend whose son has dwarfism, so I'm trying to be more aware of the preferred terminology (and that's also why I knew the answer to your question off the top of my head), but when it comes to P.C. terminology, in general, I figure just do your best, and be open to learning better ways of communicating what you want to say.

[Portia]

Yeah, that table is definitely not clear enough for my tastes. For instance, I cannot roll or curl my tongue, but everyone else in my family - half-siblings, mother - can. So clearly I did not get some copy of some gene that they did, but does that mean I am simply rr where they are Rr?Or are there epigenetic factors at work? Is this a single-gene trait?

I also have Morton's Toe - do both parents have to express the trait, or could they both be heterozygous?

When I first met my boyfriend, we were discussing his cousins' rather striking hair colors. (Anyone with a cursory familiarity with Divine Comedy or Studio C can draw their own conclusions.) He was like, "well, since red hair is a recessive trait..." I was like, "oh? indeed? you've unlocked the code to hair color heredity that has baffled geneticists for centuries? you know all the pigments present in human hair and all the gene loci? Please, share your research." Sarcastic but effective. :P

[Digit]

I can roll my tongue into a basic 'u' and flip it almost upside down, but I can't do any of the fancy tricks as in this image (I'm not even sure exactly what the bottom-left one is).

[Katya]

I can roll my tongue into a basic 'u' and flip it almost upside down, but I can't do any of the fancy tricks as in this image (I'm not even sure exactly what the bottom-left one is).

I can do the bottom-right one!

[Digit]

I guess I'm just a cloverleaf tongue level 1.

[C is for]

Gosh, can't you guys keep off topic.

[Whistler]

When I first met my boyfriend, we were discussing his cousins' rather striking hair colors. (Anyone with a cursory familiarity with Divine Comedy or Studio C can draw their own conclusions.) He was like, "well, since red hair is a recessive trait..." I was like, "oh? indeed? you've unlocked the code to hair color heredity that has baffled geneticists for centuries? you know all the pigments present in human hair and all the gene loci? Please, share your research." Sarcastic but effective.

to be fair, it is recessive, but it's not as simple as other traits http://en.wikipedia.org/wiki/Red_hair#Genetics

[Talons]

I can roll my tongue into a basic 'u' and flip it almost upside down, but I can't do any of the fancy tricks as in this image (I'm not even sure exactly what the bottom-left one is).

I'm guessing they're just rolling their tongue into a "U" on the bottom left. What's going on in top right though? They somehow made their tongue into an ear shape?

[Portia]

When I first met my boyfriend, we were discussing his cousins' rather striking hair colors. (Anyone with a cursory familiarity with Divine Comedy or Studio C can draw their own conclusions.) He was like, "well, since red hair is a recessive trait..." I was like, "oh? indeed? you've unlocked the code to hair color heredity that has baffled geneticists for centuries? you know all the pigments present in human hair and all the gene loci? Please, share your research." Sarcastic but effective. :P

to be fair, it is recessive, but it's not as simple as other traits :-) http://en.wikipedia.org/wiki/Red_hair#Genetics

That was a surprisingly solid Wikipedia article.