By Fiona Fitzsimons
There is a point that every family historian reaches when, having exhausted all the documentary evidence, s/he draws a line under research. In this last decade medical science has delivered a new research-tool—DNA testing.
Genetics is the science of inheritance. Everyone’s genome contains a wealth of information on their ancestry. DNA testing isn’t based on reading the whole genome, however, but on DNA markers, known as SNPs and STRs. SNPs show single changes that occur infrequently over time. STRs show repeat changes that happen more often. These variants in the genetic code provide an insight into family history, medical background and physically inherited characteristics like height and hair/eye colour.
There are three types of DNA tests for family historians:
Above: A representation of the double helix structure of the DNA molecule.
Genetics is a comparative science; your genes are interpreted by comparing them to the genes of other people who’ve had the same test. You might send a sample to three different testing companies only to receive three different results. Your DNA test results are an indication only. DNA testing can tell you whether you carry the gene for certain medical conditions or cancers but it won’t tell you whether that gene is ‘switched on’. This can only be determined by old-fashioned genealogical research, using documents.
What DNA testing can do is to point you in the direction of where to look. Where testing has already confirmed a relationship with a distant cousin on collateral lines, you will have evidence of what line and approximately what generation your common ancestor is on.
Scientists have recently discovered another fun thing that genetic genealogy can deliver—determining what someone might have looked like from their DNA. In future we may be able not only to recover our ancestors’ personal narratives but also to see what they looked like.
http://danielcrouch.net/Publications/FaceGenetics-12_Main+SI_website.pdf
Fiona Fitzsimons is a director of Eneclann, a Trinity campus company, and of findmypast Ireland.