I’m back, sort of, or at least this week, at least through Thursday. Anyway, time for posts, yay!
First of all, it’s 02-21-2011 or 2-21-11, that combination of digits amuses me for no significant reason. Tomorrow will be 02-22-2011. That’s a lot of two’s.
Okay, onto the real Math Monday. Dawn is a miracle child in my family. Why do I say that? Well, because the probability of her features as they exist is only 1.6%. Yup, today I want to talk about genetics and probabilities. Partially because I have been talking a bit about genetics on my job interviews, and partially because my family has always been a bit obsessed with them. Salient points:
– We call Dawn the “recessive” child due to her very visible blond hair and blue eyes, both recessive genes. She’s also a lefty. Skinny might be recessive too, we’ll see.
– Gardella used to spend hours putting together families by drawing parents then determining their genotype and using random numbers and probabilities to determine what their children would look like.
– I’m a molecular (micro)biologist. That means I work with DNA on a daily basis. I think Mendel was one awesome monk. Did you know he used peas because the monastery frowned about cross-breeding animals on their property? Good thing too, because peas have simple genes, and mouse fur colors are much more complex
Anyway, you know how a basic Punnet Square works? If not, I’ll imagine you clicked the link and now you do. Well, in our family, everyone has brown hair except for Dawn, who’s blond. That means my parents much have to be recessive gene carriers like this:
So, B is brown dominant, so BB and Bb make brown hair and bb makes blond (yes, I’m ignoring red right now, but we have no ginger genes in my family: Jewish and German!). Therefore, my parents only have a 25% chance of having a blond child.
You can draw similar squares for eye color (Mom and me are dark brown, Dad and Gardella are hazel, only Dawn has blue) and for handedness (all right-handed except Dawn). That leaves a 25% of each of those traits. So, when you combine the three 25% chances (25% * 25% * 25%) you get 1.6% or 1/64 chance. That’s why Dawn is so awesome. So is probability.
As a side note. I married a left-handed man. My chances of carrying a left-handed gene (knowing both parents are carriers) is 67%. He has two. Therefore, the chance of our child being left-handed is 33%. That’s pretty high. He also carries blond and blue-eyes genes from his father, so I may have a daughter that reminds me of my sister. Now you know how that identical cousins thing happens!