That isn't really true though. You aren't some kind of clone of your parents. Imagine that both of your parents sit down at a table. Each one has 100 dominoes in front of them. Each parent will randomly take 50 of their dominoes and put them in the center of the table. Those are your 100 dominoes. It could be that your mother has 20 "scottish" dominoes, but not a single one of those dominoes are in the set given to you. You might look at your mother's dna results and say "I'm 20% scottish!" No you're not. You got zip from the scottish side of the family.
With 23 pairs of chromosomes we have 46 dominoes each (ignoring recombination.) This changes the odds of inheriting none of your mother's Scottish dominoes from 1 in a million (2^20) to 1 in 512 (2^9).
It's been a while since I've taken high school biology, but the odds should be the same as the mother. Scottish-ness is not something that's limited to the X or Y chromosome.
Mitochondrial DNA will only come from your mother, but I don't think we're talking about that here.
What if I don't give a shit about being "20% scottish" and only care about relatives-I-didn't-know-I-had and genetically-heritable-illnesses and my parents' reports were clean?
Half siblings are probably the most interesting “relatives-you-didn’t-know-you-had” you can find! They might show up at any time, and you wouldn’t know without having your own account.
