Tag: Penetrance

Dominance, the social construct that confuses

By Razib Khan | July 25, 2011 1:31 pm

A story in The Los Angeles Times seems to point medical implications of being a sickle cell carrier, Sickle cell trait: The silent killer:

At least 17 high school and college athletes’ deaths have been tied to sickle cell trait during the past 11 years. The group includes Olivier Louis, a player at Wekiva High School near Orlando, who died on Sept. 7, 2010, following his first football practice.

You have surely heard about sickle cell anemia. It is a recessive disease which expresses in those who carry two sickle cell alleles. T-boz of TLC has the disease for example due to her homozygosity. But the allele also famously confers some resistance against malaria, which explains its concentration in regions which have historically been malarial. Sickle cell is arguable the classic case of heterozygote advantage driving the emergence of a recessive disease. The frequency of the allele is balanced at the equipoise between the proportion of people who are more susceptible to malaria if its proportion is too low and those who express sickle cell anemia if its proportion is too high. This advantage is obviously context sensitive. The standard assumption is that in a non-malarial environment selection pressure against anemia will drive the frequency of the allele down over time as heterozygotes don’t impose a floor in the proportion of the mutant allele. This seems to have occurred among African Americans, they’re ~80% West African, but their frequency of the sickle cell anemia allele is less than {0.80*(the West African proportion)} from what I know (remember that the median number of generations which an African American’s black ancestors have been in the USA is probably ~10).

Read More

CATEGORIZED UNDER: Genetics, Health, Medicine
NEW ON DISCOVER
OPEN
CITIZEN SCIENCE
ADVERTISEMENT

Discover's Newsletter

Sign up to get the latest science news delivered weekly right to your inbox!

Gene Expression

This blog is about evolution, genetics, genomics and their interstices. Please beware that comments are aggressively moderated. Uncivil or churlish comments will likely get you banned immediately, so make any contribution count!
ADVERTISEMENT

See More

ADVERTISEMENT

RSS Razib’s Pinboard

Edifying books

Collapse bottom bar
+

Login to your Account

X
E-mail address:
Password:
Remember me
Forgot your password?
No problem. Click here to have it e-mailed to you.

Not Registered Yet?

Register now for FREE. Registration only takes a few minutes to complete. Register now »