# DNA Inheritance- Math vs. Biology

After doing some statistical analysis of the raw math involved in DNA contributions, I would like to understand the scale of the biological factors. I know that 99% of the human genome is identical in all human beings, so genetic recombination and gene conversion should be irrelevant in those areas. I know that recombination occurs at different rates depending on the chromosomes and loci. But what is the average order of magnitude? That is, if I know that a chromosome mainly came from Grandma, how much of it is likely to be from Grandpa? .1%, 1%, 10% ? And, does the age of the male affect the rate of recombination to a measurable degree (in spermatozoa only, as body cells would not affect inheritance).

• What do you mean by "the scale of the biological factors"? And what do you mean by "the average order of magnitude"? As you just said, differences are tiny between any two randomly drawn humans (in DNA sequence), so if this is your 'metric' there can't be any differences in 'orders of magnitude'. If you only ask about the fraction of the particular DNA (in chromosomes) that was copied into your own genome from your ancestors, then it is roughly half from your parents, a quarter from your grandparents, and so on. Commented Oct 5, 2019 at 21:27
• DNA tests are done only on the variable segments: It would be pointless to say "you're a 99% match to this other sample, it must be your identical twin." Using the "average" of the actual distribution is misleading. Only 32.24% of people inherit between 23.91% to 26.09% from a grandparent while 90.69% inherit somewhere in a range of 17.39% to 32.61%. Commented Oct 6, 2019 at 1:54
• Agree, so, what is that you are asking then? Commented Oct 6, 2019 at 1:56
• DNA testing is in its infancy, and different labs use different protocols for their tests and different models to report results. 2 samples from ME will not show a 100% match to MYSELF. The zygote that turned into my mother, say, had 23 intact chromosomes from each of her parents. When my zygote was formed, recombination may have occurred in the specific ovum that made me. Take chromosome 1- the main body of which came from her father. Is it likely to be 99.9% grandpa with .1% recombined from grandma, or more in the 90% grandpa 10% grandma range? Commented Oct 6, 2019 at 2:25