Monday, 3 December 2007

Could Dick Eastman be misleading us?

I've learned a lot from reading Dick Eastman's Online Genealogy Newsletter over the years, both the free and subscription versions. He's a tremendous asset to the community and I rarely miss a posting.

BUT

I was surprised to find myself doubting his opinion recently.

I watched a video, available here, of a talk he gave at BYU entitled Putting the Genes in Genealogy. It started with him reflecting on why people investigate their roots, making a contrast between name collectors and those who want to know more about the ancestors in depth including their role in a larger historical context.

Then he got into health and family history, and genetics. He pointed out that a study of elevated occurrence of hemophilia, a genetically linked affliction, in Maine had been traced by genealogical studies to an originating family in the state. He used that to argue that the study of genealogy will be of great assistance in helping people assess their susceptibility to genetic disease.

You only inherit one of each of the 22 chromosomes from each of your parent's pair, it may or may not be the one that's defective. There is no information on which one it is in a genealogy study so the best you can get from a genealogical study is a likelihood. However, once the cost of genetic testing declines substantially, and that's an ongoing process, everybody will be able to get their own precise DNA evaluation for genetic disease susceptibility. In his eagerness to find a rationale for studying your roots Dick overstated the case.

I must be quick to point out that genetic susceptibility is thought to only part of the picture. Lifestyle and diet are also important factors weighing in the balance of whether a disease develops.

2 comments:

Hsien-Hsien Lei, PhD said...

Hi John, Thanks for linking to the video at EyeOnDNA.com. I just want to point out that tracing the family history of hemophilia in a pedigree is somewhat different than doing the same for diseases such as diabetes because hemophilia is an X-linked disease that predominates in males who inherit the defective X chromosome from the mother. Because of this important distinction, it is possible to trace the spread of hemophilia through a family history. A prime example is hemophilia in the family history of European royalty.

As to not forgetting the importance of lifestyle factors in the development of disease, I totally agree with you. For complex diseases, such as diabetes, heart disease, and cancer, both genetic and environmental risk factors are critically important. However, there are monogenic diseases, such as hemophilia, in which one defective gene is all it takes for a person to develop a serious disease. In fact, over 10,000 human diseases are caused by a single genetic mutation.

I'm not very much involved in the genealogy community (although I find genetic genealogy absolutely fascinating) so I cannot vouch for Dick Eastman but based on what I've seen of his work, I wouldn't discount his credibility based on these specific statements you discussed.

Thanks again for visiting Eye on DNA! :)

Hsien-Hsien Lei, PhD said...

Oh, this is probably just a typo but I wanted to point out that we have 23 pairs of chromosomes including the sex chromosomes. So that's 22 autosomal chromosomes from each of our parents and 1 sex chromosome.