Testing the accumulation of harmful mutations during spatial expansions using exome sequencing

This project explored how the settlement history of Quebec may have shaped the genetic diversity seen in the population today. When a new territory is colonized gradually, the first families to move forward—those living on the “expansion front”—often form small, isolated communities. In such conditions, natural selection is less effective, which can allow slightly harmful genetic mutations to accumulate more easily. This phenomenon is known as the expansion load.
Using genetic and genealogical data from CARTaGENE participants linked to the BALSAC database, the research team compared individuals whose ancestors lived mainly at the expansion front with individuals whose ancestors remained in the core regions of Quebec. The analysis showed that descendants of pioneer families tend to carry a slightly higher number of rare and potentially damaging mutations.
These findings help explain why certain recessive genetic diseases are more common in regions that were settled recently, such as the Saguenay–Lac-Saint-Jean. The project highlights how demographic history can influence genetic health in present-day populations.

• Genetics and genomics
• Methodology and biostatistics

• Biological samples
• Questionnaire data