Several recent studies suggest male-line generations, from father to son, are always longer on average than female-line  generations, from mother to daughter. They show, too, that both are longer than the 25-year interval that conventional wisdom has assigned to a generation. The male generation is at least a third longer, the female generation is longer by perhaps half that amount thus male line 3 generations per century and matrilineal 3.5 per century. Mine will be 3 per 100 years

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How much of your genome do you inherit from a particular ancestor?
Posted on November 4, 2013by cooplab
How much of your genetic material do you inherit from a particular ancestor? You inherit your mitochondria through your matrilineal lineage (your mum, your mum’s mum, your mum’s mum’s mum and so one) and your Y chromosome from your patrilineal lineage, but how is the rest of your genome spread across your ancestors in any given generation?

A generation ago you have two ancestors, your parents, two generations ago you have four grandparents (ignoring the possibility of inbreeding).
Each generation we go back your number of ancestors doubles, such that your number of ancestors k generations back grows at 2^k (again ignoring the possibility of inbreeding, which is a fair assumption for small k and if your ancestry derived from a large population).

However, you only have two copies of your autosomal genome, one from your mum one from your dad. Each generation we go back halves the amount of autosomal genome you receive, on average, from a particular ancestor. For example, on average 50% of your autosomal genome passed on from your mother comes from your maternal grandmother, 50% comes from your maternal grandfather. This material is inherited in large chunks, as chromosome fragments are inherited in large blocks between recombination events.

As you inherit autosomal material in large chunks there is some some spread around the amount of genetic material you receive; e.g. you might have inherited 45% of your autosomal material from your maternal grandmother, and 55% from your maternal grandfather. In my last post on this topic I looked at distribution of how much of your autosomes from grandparents, and I talked about why it was vanishingly unlikely that you received 0% of your genome from a grandparent.♦️My dna y from Root Adam

♦️My dna mt from Root Eve

♦️My dna autosomal
Autosomal tests give you a picture of your genetic heritage from the past five generations of your family. They also report on your ‘recent’ ancestors: Those that lived in the thousand year period before the era of mass migration circa 1850. An autosomal test may also be referred to as a DNA origin test.♦️My Ancestry .co.uk
This type of test, also known as a DNA origin test, looks specifically at SNPs and will commonly tell you which population groups or ethnicities your DNA is associated to and in what proportions. Most autosomal tests look for 600,000 to 1,000,000 SNPs, and will find approximately 100,000. These 100,000 SNPs will be cross-referenced with the reference populations that the company has access to, and this will allow them to report on your ‘ethnic breakdown’. Like mitochondrial and Y chromosome tests, some companies will use your autosomal results to help you find your living relatives.♦️Statistics & Glossary

 

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