Many commercial DNA tests offer up a massive wealth of information on the tester’s ancestry, however some information is sometimes misinterpreted when researching DNA tests. A lot of people seem to think that if a male takes a test they can only see their Paternal Ancestry and if a female takes a test they can only see the Maternal part. This is not necessarily true, there are three main types of DNA test. Autosomal, Y-DNA and mtDNA. Y-DNA is one that is only available to a male as it tests the Y Chromosome which females do not possess. mtDNA and Autosomal tests are available to both genders. mtDNA tests the Mitochondrial DNA in our cells which is handed down from Mother to Child relatively unchanged, which gives the taker a maternal genetic make up that has been passed directly down the Maternal line.
Autosomal is the main DNA test. It tests the 22 Autosomes, which are the Non sex Chromosomes (X/Y). This means we get a much broader test which can show a much more recent DNA structure compared to the Y-DNA and mtDNA tests tracing back to thousands, sometimes tens or hundreds of thousands of years ago.
A lot of people also think that if two siblings test then they will get the same results. This is completely untrue, whilst it should be similar, Siblings only share around 50% of the same DNA on average as they could inherit different chunks of DNA from each parent. This could mean that one sibling might inherit a much larger chunk of DNA which is widely accepted to originate in Scandinavia where as another may inherit a much larger chunk that originated in the Iberian Peninsular meaning their results could show wildly different ancestry compositions.
Of course testing parents is a sure way to find out exactly where a child gets it’s ancestry from and seeing the exact parts of their genetic make up they inherited from each parent. With this in mind there are a few things we can be sure of between a brother and a sister.
- Both children will have identical mtDNA, so only one would need to take an mtDNA test to find out about each. This is not particularly useful for research as it only deals with the very distant past however.
- Only a son will have Y-DNA, so whilst the sister would not actually have anything in common here, it would show her father’s direct line.
- Both will inherit overlapping Autosomal DNA and the more siblings/family members tested the better overall picture you would have. This is the most useful for identifying people with shared ancestry.