Understanding Genetic Mixing Through Migration

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Understanding Genetic Mixing Through Migration

http://www.medicalnewstoday.com/articles/191663.php

Understanding the genetic ancestry of mixed populations, such as those found in

North America, can not only help to detect their origins but also to understand

the genetic basis of complex diseases, a scientist told the annual conference of

the European Society of Human Genetics (Saturday June 11). It is the first time

that the genomes of individuals of admixed ancestry have been sequenced in such

detail, says Dr. Francisco De La Vega of Life Technologies, City,

California, USA.

Working with Professor Bustamante and his team in the Department of

Genetics at Stanford University, the scientists analysed the genomes of two

people - one of African-American and one of Hispanic-Latino origin. The majority

of the personal genomes sequenced to date come from individuals of either

European, African, or Asian descent, because it is in these groups that most

genetic disease association studies are being carried out. However, populations

where genetic mixing through migration has taken place relatively recently make

up a sizable proportion of the world's population, and have been not been well

studied to date because of the complexity of dealing with the contributions of

genes from different ancestries in disease.

" We set out to provide a better understanding of the genome structure in admixed

populations by sequencing one African-American and one Mexican sample " , said Dr.

De La Vega. " By analysing genetic variants in mixed people whose frequency

differs in the ancestral populations, we can work out the ancestry of different

chromosomal segments in an individual. This has already been done in a number of

different ways. The difference with our work is that, by using whole genome

sequencing using the SOLiD™ System, we can greatly increase the resolution of

our analyses and achieve a very much clearer picture of the ancestry of genome

sequences for the individuals studied.

" We already know that present-day African-Americans trace their ancestry to a

rich mosaic of migrants from the mainly West African and Northern European

populations who settled in North America and the Caribbean. Mexicans, on the

other hand, are descendants of Meso-American indigenous populations

& #65533; & #65533; " themselves derived from population migrations from Asia

(through the Bering straits) - and largely Southern European (mainly Spanish)

settlers " , said Dr. De La Vega. " But the added value of our research is that we

can show the approximate number of generations at which the genetic mixing

occurred, estimate the rate at which admixture occurred, and understand better

the genetic diversity in the ancestral populations. "

To date there are few comprehensive studies of genetic diversity in native

populations in the Americas, and by analysing them scientists can begin to piece

together the population history of both the admixed and indigenous populations.

They can also begin to analyse the contribution of native American genetic

variants to the disease burden in the Americas of today, something which at

present is relatively unknown.