darkerhorse wrote: 30 Mar 2021, 17:22
So, if my father was 100% Sicilian and my mother was 0% Sicilian, I and my siblings should have 50% Sicilian ancestry in our DNA.
What could cause that to vary, assuming my parents' ancestry is correct?
Also, what company/test would be best to answer that question of percent Sicilian ancestry?
Read up on the concept of recombination. I'm by no means an expert, but I think in your extreme case you would have to get 50% Sicilian (Italian) from your father. However it's rare to see a person truly 100% of any ethnicity, so you have to also (first) consider that oddity (unlikely occurrence).
I think a better example is if, say, your father was 30% Italian. You would, of course, get 50% of your (total) Autosomal DNA from him, but that does not mean, for example, that you'll get half of his 30% Italian, or 15% Italian. The actual percentage of Italian that you receive from him can be anywhere between 0% and 30%.
A further example is how much Italian a person would inherit from a given grandparent. For me, I have one Sicilian grandparent (Messina). You would think me and my siblings would each get exactly 1/4 or 25% of that (the concept of averages) from all four grandparents. That's not the case. Depending on the DNA testing site you go to, I have around 22-27% Italian, whereas my sister appears to "only" have around 15%-20%.
The bottom line is that, through recombination, "crossover" occurs so a person can get more or less than the 25%. The only constant is that the percentages inherited from either both of your maternal grandparents or both of your paternal grandparents must add up to 50%.
