[Ashkenazi-Q] Left handedness ( was MCR1within Q1b)
- Adam, Thank you for taking the time to do the research and share. A very interesting read.BJ----- Original Message -----From: AdamSent: Wednesday, November 18, 2009 1:50 PMSubject: [Ashkenazi-Q] Left handedness ( was MCR1within Q1b)
First off, an aside - my FTDNA results are starting to trickle in. So far, with the exception of some nomenclature differences, they agree exactly with the Genebase results. I just joined the Q project in FTDNA. I have 2 matches at a distance -1 with 37 Y markers.
Even though I am left handed, I had never looked up the genetics of left handedness. Genes are not always the answer as to why people turn out like they do. So, i went and did a brief literature search . . .
Even though we have all heard of families with large numbers of lefties, the best available data to date shows a very minimal contribution of genes to a person being left- or right- handed.
The most common way of doing this is through studies of twins, and seeing how many twins are "concordant" with each other handedness (ie, both left- or right- handed -vs- one of each).
Vuoksimaa E, et al. Neuropsychologia. 2009 Apr;47(5):1294- 301.
Ooki S. Twin Res Hum Genet. 2005 Dec;8(6):649- 56.
Genetics are not always black and white (or red in the case of MC1R, as Rebekah pointed out). Some examples:
- You can have a gene change and not have the feature (phenotype) of the gene change = incomplete penetrance.
- Multiple genes can cause the same phenotype = phenocopies
- Multiple genes can contribute
to (or degree of) a phenotype = complex traits. Big example is hypertension
(high blood pressure) - lots of genes, and the environment,
- Having a "risk gene" doesn't
mean you will get the disorder. You might just be at a slightly higher risk
than the portion of the population that doesn't have that risk gene. This is
one of the major reasons the US govt passed the Genetic Information
Nondiscrimination Act (GINA).
- Some phenotypes can have a
genetic, or a "random", cause, and we can't always tell which it is for a
particular person, especially in common disorders. Big example is breast
cancer. But . . . sometimes our describing something as "random" just means
we haven't dissected out all the minor contributing genes. But remember . .
. you can have a minor contributing risk gene change, and never get the
Have a great day . . . Adam