I am 3/4 Italian, and 1/4 Polish. My dad is half Polish, half Italian, my mom is 100 percent Italian. Now that would make me 3/4 Italian, and 1/4 Polish. But is this true in terms of genetics. Does the Polish outweigh the Italian or is the Italian more predominant. Does it work in terms of percentage or is it just a random outcome which side’s features and traits one will inherit from their parents?
For one thing, there’s going to be a lot of overlap between the genes of Italians and Poles. As Europeans, they are going to share a lot of alleles. Besides that, the Poles are going to have plenty of genes that might have originated in Germany, Russia, or for that matter Central Asia, and the Italians may have some genes from Vikings etc.*
This said, you inherit half your chromosomes from your mother, and half from your father. However, which genetic material you receive from each is basically a random mixture of what they received from their parents, both because chromosomes assort independently and because chromosome pairs undergo crossing over of genetic material during the formation of gametes.
The upshot of this is that although 100% of the genetic material you receive from your mother will be of “Italian” origin (whatever that may be in this case), what you receive from your father (aside from the X chromosome) will be a random combination of “Polish” and “Italian.” In theory your genetic material could be anywhere from 50% Italian and 50% Polish to 100% Italian (although in practice most likely it will be close to 25/75%).
*I went to a talk by an Italian geneticist a couple years ago. Although he said his family can be traced back many centuries in Italy, analysis showed his mtDNA was of Middle Eastern origin (probably Jewish), and his X-chromosome was from Central Asia (perhaps a legacy of Mongol incursions into Europe).
Every time someone produces an egg or sperm, it’s luck of the draw which pieces genetic material (of their mother’s and father’s) goes into that sperm or egg. It’s half the genetic material, but of assorted pieces randomly selected to be from one parent.
You could theoretically receive from your mother only her share of her mother’s DNA (or of her father’s), but the odds of the mix separating out like that are pretty close to zero.
We have 46 chromosomes n 23 pairs, one half of the pair from the mother and half from the father. As I understand from a previous discussion on genetics, it’s not unusual for a set of paired chromosomes to “mix and match” pieces during replication, so an individual chromosome passed on may contain a mix of both parents’ genes. the unique one is the X and Y - a female contains two X (one from each parent) and a male an X from the mother and the Y from the father.
Thus, as I understand it, the Y has no match in the pair (nor does the X, in a male) and the usual possibility of mixing genes with the complement chromosome does not happen, the Y survives pretty much intact from generation to generation.
All of the above subject also to occasional random mutations during the DNA replication too.
So based on statistics, you likely have a random mix of the source gene pool(s) which would be a roughly even distribution of your ancestors, so 3/4-1/4 is probably as good as you can estimate. However, traits attached to the Y chromosome are definitely from the male line all the way down. What that involves? I don’t know.
Of course, “Polish” is putting an arbitrary label on what may be 2 very different gene pools depending on each area and its history, unless the 3 grandparents came from the same neighbourhood of Poland; and that also depends on other things, like whether there were ethno-cultural-religious divisions not crossed-pollinated, so to speak, in the old country but ignored once they arrived in America.
So the basic understanding is that your most recent ancestors have a greater effect on your genetic makeup than a single person 600 years ago would?
Of course. Assuming a generation as 25 years, 600 years was 24 generations ago. That person would have been only one of more than 16 million possible ancestors you would have had at that time. (Of course, due to pedigree collapse the actual number of ancestors would be much smaller.)
Your parents each contribute half your genome. Your grandparents on average contribute one quarter. Your 22nd great-grandparent contributed on average 1/16,000,000th. (Some would have contributed more, others might by chance contributed zero, having all of their genetic material eliminated from your lineage, even though they are your ancestors.)