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Genetic Heritage, MT DNA and Y-Chromosomes

Presentation by Christoff Erasmus: 13 July 2013
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Christoff Erasmus is currently doing a PhD and his focus is on combining genealogical records and genetic data for the Afrikaner population. By taking the genealogical records into consideration and collecting DNA marker data, we can estimate population genetic parameters, like mutation rates and nonpaternity. We also aim to create a publicly available database explaining the genetic make-up of the Afrikaner population and linking typical y-chromosome STR profiles to certain surnames.
In his presentation Christoff started by explaining the lifeline of our DNA. He mentioned three types of DNA that is of importance in genetic studies, i.e. Autosomal, Y-chromosome and the Mitochondrial DNA. The question can be raised why compare y-chromosomes and genealogical pedigrees. The family researcher can use this information to find links to the

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founding father and it can also be used to calculate mutation rates that are useful in the forensic environment for paternity testing and case work. Take note that the y-chromosomes move along the paternal lines whilst the mitochondrial DNA is passed along the maternal line from mother to daughter, but will also be found in the sons of a mother.
In his study Christoff used samples of 185 volunteers from 20 pedigrees to establish the y-chromosome heritage, mutation and nonpaternity rates in the Afrikaner population. The results obtained however put the researcher in a position to allocate the tested individuals to various haplogroups (in genetics it is a combination of DNA sequences at adjacent locations on a chromosome) such as E1b1b; G2a; R1a etc. The concentration of these groups in specific regions of the world can thus indicate the origins of a specific family. The founding fathers of the 20 pedigrees originated from Europe based on the y-chromosome results.
Genealogical research indicates that, on average, 94% of the Afrikaner founders are from European countries. If the founding fathers all originated from Europe, it means that as much as 12% of the founding mothers could be from non-European origin. The mitochondrial DNA gives us the genetic input from the founding mothers of a population. Based on mitochondrial results, the Afrikaners had an 18% non-European genetic input for the founding mothers of the population. The genetic results indicate a 1.5 times higher non-European genetic input into the population compared to the genealogical estimates.