Monday, June 7, 2010

DNA Testing presented by Thomas H. Shawker, MD

Thomas H. Shawker, MD  is chairman of  the NGS Committee on Genetic Genealogy and a physician at the National Institutes of Health with over 200 scientific publications. He wrote a book titled Unlocking Your Genetic History: A Step-by-Step Guide to Discovering Your Family's Medical and Genetic Heritage.
I attended two sessions taught by him.

1. The ABCs of DNA Testing. This session was the basic introduction to DNA testing. We learned about the structure of DNA molecules and about the two types of ladder rungs T-C and G-A. We learned about the 23 pairs of chromosomes and the sex chromosomes (XX=female and XY=male). Y-Chromosome genetic testing is used to identify father-son relationships. It is useful but we need to remember that there are circumstances where it is not accurate.
We also learned about Mitochondrial DNA (mtDNA) which is DNA outside the nucleus of cells and is passed to children from their mother so it is useful to identify mother-daughter relationship also with limitations. We also learned about haplotypes, an individual's series of markers. Haplogroups are associated with ethnicity. They originated with Y chromosomes and mtDNA thousands of years ago and are defined by SNP (Single Nucleotide Polymorphism). Dr. Shawker used the Irish Modal Haplotype (IMH) to show how groups of people migrated across Europe in pre-Roman times.
2. DNA Testing for Race, Ethnicity, and Ancestry. This class built on what was presented in the first class. We learned more DNA Markers which have Base Sequence Change  or Base Length Change. A SNP (Single Nucleotic Polymorphism) is the change of one base. A STR (Short Tandem Repeat) is a Base Length Change. Human DNA has a very slow mutation rate. The people of Africa have the most diversified DNA in the world. Groups like the Jewish people and the Amish people have the least diversity.

Dr. Shawker was an excellent speaker and showed interesting and entertaining slides. He explained things clearly. The group was very interested and asked lots of questions in the question and answer period at the end.

According to Dr. Shawker, DNA Testing is getting better and the price is dropping as time goes by. I do not see a need to do any DNA Testing in my immediate research work, so I will wait and see what happens with this revolutionary scientific field.

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