@rojo Everyone always gets exactly 50% of their DNA from their mother and 50% from their father except in very rare circumstances such as an extra chomosome. That’s because an egg or sperm copies 50% of the producer’s DNA when it is formed, so when an egg and sperm join up, that’s what’s there (again, barring very unusual sperm/egg or something).
When your DNA test comes back with 41% Irish and 19% Scandinavian, that’s because you’ve switched what you were talking about, not because you’re an uneven mix. Your ancestors were not really 100% genetically “English” and “Irish”, for a few reasons. You probably don’t have DNA tests for them, and if you ran them, they’d probably show a mix of specific origins too because:
* Their ancestors may have stayed in England and Ireland as far as you know, but the people in Ireland and (especially) England have a mix of origins, whether Vikings, Normans, Romans, or other travelers, or simply that if you go back far enough, other places and times before any of those place names were used.
* The way DNA is labelled as being from a place is a statistical labeling approximation where a subset of genes are known to have been found in the population at a certain place and time, to aid in estimating where a sample’s ancestors may likely have been from based on statistics. It’s not like each piece of DNA can be labeled as a specific nationality. A lot of genes don’t have a known specific time/place association.