Genetic Variance Between Pops as compared Within Pops

[Simfish]

As it often said, the majority of the variation in the human genome is due to intra-group variation, not inter-group variation (I think .85 is the number due to intra-group variation). I know what this intuitively means, but can anyone explain to me what it rigorously means? (in statistical terms?)

 

[EnumaElish]

I don't know how group is defined, but it doesn't matter as long as YOU know.

Suppose you have a numeric index of human genome code for each individual i in group g. Let that index be Y: H --> R. That is, for genome h in H, Y(h) is a real number. Each group is a subset of H. Subscript i indexes the h's in group g; i = 1, ..., I_g where I_g is the number of h's in group g. There are k groups.

A regression equation of the following form is estimated:

y_i,j = a + b₁d₁ + ... + b_kd_k + u_i,j

where the dependent variable is Y(h_i,j) = y_i,j and the independent variables are the d's; u is the error term. For each g, d_g = 1 if j = g (that is, h_i,j is in group g), d_g = 0 otherwise. The R^2 statistic of the estimated equation is expected to be 0.15 (a poor fit).

 

[tacman]

In statistical terms, the statement that the majority of the variation in the human genome is due to intra-group variation means that within a given population, there is a higher amount of genetic variation between individuals than there is between different populations. This is often measured by a statistic called Fst, which quantifies the genetic differences between populations. A high Fst value indicates a greater degree of genetic variation between populations, while a low Fst value indicates a higher degree of genetic similarity within a population.

In this case, an Fst value of 0.85 suggests that 85% of the genetic variation in the human genome can be attributed to differences between individuals within a population, while only 15% can be attributed to differences between different populations. This can be further explained by the fact that humans have a relatively recent common ancestor and have been evolving in a relatively similar environment, leading to a higher degree of genetic similarity between populations.

Overall, the statement highlights the importance of considering genetic variation within a population rather than solely focusing on differences between populations. It also highlights the fact that there is more genetic diversity within a population than there is between different populations, emphasizing the need to study and understand genetic variation at a local level.