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Irish genetic patterns rooted in historical migrations

Researchers at Trinity College Dublin have taken a closer look at the genetic diversity of the Irish population. The experts have discovered a hidden genetic footprint that was formed by both geography and historical migrations.

Ireland has been inhabited for 10,000 years. While cultural and geographical differences have been established, there has been no distinction made between various genetic groups across the country.

The current study assembles a new image of the genetic landscape of Ireland which is quite complex. The findings clearly show the genetic signatures left behind within Irish populations by historical migrations.

“This subtle genetic structure within such a small country has implications for medical genetic association studies,” said study co-author Ross Byrne. “As it stands, current corrections for population structure in study designs may not adequately account for this within country variation, which may potentially lead to false positive results emerging.”

The researchers analyzed genetic variation across nearly 1,000 Irish genomes and compared them with over 6,000 genomes from Britain and mainland Europe. The experts discovered 23 distinct Irish genetic groups separated by geography.

The groups were found to be the most discernible in western Ireland, but less prominent in the east. In eastern Ireland,  historical migrations have eliminated the genetic divisions.

Genetic contributions from British people were found to drop off in populations to the west. Genetic input from Europe revealed the timeline of the historical migrations of the Norse-Vikings and the Anglo-Normans to Ireland, and these dates were consistent with historical records.

“The long and complex history of population dynamics in Ireland has left an indelible mark on the genomes of modern inhabitants of the island,” said study co-author Russell McLaughlin.

“We have shown that, using only genetic data, we can accurately reconstruct elements of this past and demonstrate a striking correlation between geographical provenance and genetic affinity. Understanding this fine-grained population structure is crucially important for ongoing and future studies of rare genetic variation in health and disease.”

The study is published in PLOS Genetics.

By Chrissy Sexton, Staff Writer

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