Are DNA tests rub­bish?

The Citizen-Record (Cumberland) - - COMMUNITY - Diane Tib­ert Diane Lynn McGyver Tib­ert, au­thor of Scat­tered Stones, is a free­lance writer based in Cen­tral Nova Sco­tia. Visit her Roots to the Past blog (https://root­stothep­ast.word­ to learn more about her ge­neal­ogy writ­ing.

Over the past 20 years, the num­ber of ge­neal­o­gists who use DNA tests as one of their tools for re­search has in­creased sub­stan­tially. For this test, the more peo­ple in the world who par­tic­i­pate, the bet­ter the re­sults be­come for ev­ery­one. Re­sults are not per­fect and there is much to learn about how DNA can bet­ter help in­di­vid­ual re­searchers and in­crease our un­der­stand­ing of eth­nic ori­gin.

The in­crease in DNA test­ing stems from ge­neal­o­gists shar­ing their re­sults and the hype of com­mer­cials that claim peo­ple can find their an­ces­tors over the week­end or with one sim­ple test. The week­end ge­neal­o­gist war­rior con­quer­ing their fam­ily tree in 48 hours is far from ac­cu­rate.

DNA tests for ge­neal­ogy re­search is sev­er­ally lim­ited by the low num­ber of hu­man DNA sam­ples on file. To be ex­cep­tion­ally ac­cu­rate, we’d need DNA sam­ples from all eth­nic groups across the globe span­ning the last 400 years, be­fore peo­ple be­gan to mass mi­grate.

DNA links us to our an­ces­tors like no other body fea­ture be­cause we get an equal amount of chro­mo­somes, which makes up our DNA, from each of our par­ents. In the­ory, our DNA pro­vides a road map to our an­ces­tors but in re­al­ity, there’s not enough known about it or enough sam­ples through­out the world to cre­ate the map.

There’s been re­search com­pleted that sug­gests we carry mem­o­ries in our DNA, and that we are con­di­tioned by those mem­o­ries. Fear is one of our strong­est emo­tions, and it is be­lieved if our an­ces­tors feared some­thing — for ex­am­ple preda­tory an­i­mals — we may also have that fear.

In my mind, it is sim­i­lar to in­stincts. Moth­ers in­stinc­tively know to care for their child, and fa­thers in­stinc­tively know to pro­tect their fam­i­lies. Per­haps these in­stincts were passed through the gen­er­a­tions through DNA.

There are three types of ge­netic an­ces­try test­ing used in ge­neal­ogy.

The Y chro­mo­some test tracks the Y chro­mo­some that is only passed through the males of the fam­ily. Women don’t carry this chro­mo­some, so only male mem­bers of the fam­ily can have this test done.

The mi­to­chon­drial DNA test pro­vides data on the fe­male lines of the fam­ily be­cause the mother passes on her mi­to­chon­drial DNA. How­ever, since both male and fe­male re­ceive it, sons and daugh­ters can use this test to trace their mother’s line.

The third test is sin­gle nu­cleo­tide poly­mor­phism.

It eval­u­ates a large num­ber of vari­a­tions across a per­son’s en­tire genome, trac­ing the lines of both par­ents. You’ll of­ten see re­searchers post these re­sults, stat­ing they are 25 per cent of this and 35 per cent of that eth­nic group.

In a BBC Ra­dio 4 in Four in­ter­view ( pro­grammes/p05z4m57) with ge­neal­o­gist Deb­bie Kennett, the in­ter­viewer asked if DNA re­sults were rub­bish?

Kennett ex­plains DNA re­sults are a tool, but they can’t re­place ac­tual re­search be­cause DNA looks at the dif­fer­ences in pop­u­la­tions one thou­sand years ago or more, not in­di­vid­ual fam­ily lines. They can pin­point a con­ti­nent, but nar­row­ing DNA to a par­tic­u­lar coun­try is tough.

With re­gard to re­ceiv­ing dif­fer­ent re­sults when hav­ing tests done by dif­fer­ent com­pa­nies, she said each com­pany col­lects dif­fer­ent pop­u­la­tion ref­er­ences, and they use dif­fer­ent al­go­rithms.

For ex­am­ple, if a com­pany has com­pleted 100,000 DNA tests and the ma­jor­ity of those who pro­vided DNA were from Ire­land, United King­dom and Europe, then there are no DNA ref­er­ences from ev­ery other place on the planet.

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