Heritage

[JustMeSee]

Hello all.

I have a question. There is a company advertising on Facebook that does DNA testing for geographic heritage.

They give numbers like 11 percent Irish, 44 percent Italian, and 55 percent Kenyan.
This doesn't seem to be possible or accurate. My understanding is it would accurately be 100%, 50%, and further exponents of 1/2. That is 0.5^x. x being a positive integer.

We have half from each parent, quarter from each grand parent, and so on.

Please correct my understanding .

 

[Elendur]

I don't know the specifics but I'll take a stab at it.

You're essentially sensible to think in terms of exponents of 1/2, but don't forget the summing.

Say that
my first parent is 50% swedish and 50% finnish
and that
my second parent is 25% swedish, 25% russian and 50% japanese.

That would make me 12.5% russian, 25% japanese, 25% finnish and 37,5% swedish. (summing and then dividing by two, essentially taking the mean of each)

This is of course a crude modelling and most surely not what they're using, due to criteria of belonging to a country etc.

But since you now have not only the space of exponents of halves, but also the resulting space of the summed values you could get an arbitrary distance from and number within the interval (0,1).

Hope this answers the question

 

[Michael]

Hello all.

I have a question. There is a company advertising on Facebook that does DNA testing for geographic heritage.

They give numbers like 11 percent Irish, 44 percent Italian, and 55 percent Kenyan.
This doesn't seem to be possible or accurate. My understanding is it would accurately be 100%, 50%, and further exponents of 1/2. That is 0.5^x. x being a positive integer.

We have half from each parent, quarter from each grand parent, and so on.

Please correct my understanding .

It probably depends on how many generations back we're talking, and how much genetic material is actually transferred to every child. You're correct that we "typically assume" a 50/50 split with respect to DNA when talking about our personal DNA heritage, but that's really just an oversimplification to begin with. We all end up with the same mitochondrial DNA for instance.

 

[JustMeSee]

Thanks. This is helpful in my consideration.

I am not that interested in my distant ancestry. I am fine with my parents and grandmother's say on the matter. It is good enough for me. Borders and continents mean little to me. It really isn't my identity.

I am interested in learning more about genetics in general.

 

[sfs]

By the way, you don't actually get 25% of your genetic material from each grandparent. That's the average amount you get (ignoring the different sizes of the sex chromosomes), but the exact amount varies, depending on where chromosomes cross over in meiosis.

 

[gnomon]

It might mean something if genetics equaled ethnic identity. But it doesn't. So it doesn't mean much of anything. Since the definition of ethnicity is a complex idea involving religion, language, general culture, politics, etc. and genetics has not ever been shown to be a determinate in identifying these factors.....there you go.

It seems we have time stamped the last few centuries after the rise of European nationalism as the time frame in which all cultures are defined. Never mind the vast amount of cultural differences within those nations and the even greater cultural variations prior to the rise of nationalism.