What can DNA tests really tell us about our ancestry? - Prosanta Chakrabarty

Recent questions

• Why do siblings show different ancestry percentages in DNA tests?

  Siblings can display varying ancestry percentages in DNA tests due to recombination, a process where chromosomes exchange sections before conception. This results in unique combinations of DNA in each sex cell, leading to differences in genetic makeup between siblings. For example, one sister may appear more French in DNA tests because she inherited a higher representation of French ancestors through recombination.

• How do DNA tests determine ancestry?

  DNA tests determine ancestry by comparing genetic markers with individuals currently living in a specific region, such as France. By analyzing these markers, the tests can estimate the geographical origins of a person's ancestors. However, the accuracy of these results is limited by the representation of populations in the DNA database. Indigenous populations are often underrepresented, which can impact the precision of ancestry estimates.

• Can DNA tests accurately identify all ancestral backgrounds?

  DNA tests may not be able to accurately identify all ancestral backgrounds due to limitations in database representation. While these tests can provide insights into a person's genetic heritage by comparing genetic markers with individuals from specific regions, the accuracy of results is influenced by the diversity of populations included in the database. Indigenous populations, in particular, are often underrepresented, which can affect the ability of DNA tests to identify all ancestral backgrounds.

• What is recombination in DNA and how does it affect siblings?

  Recombination in DNA is a process where chromosomes exchange sections before conception, resulting in unique combinations of genetic material in each sex cell. This process affects siblings by creating differences in their DNA makeup. As a result, siblings can display varying percentages of ancestry in DNA tests, as recombination leads to distinct genetic compositions between siblings. This variation can explain why one sibling may appear to have a higher representation of a specific ancestry compared to another.

• Why are indigenous populations often underrepresented in DNA databases?

  Indigenous populations are often underrepresented in DNA databases, impacting the accuracy of ancestry estimates. This underrepresentation occurs because DNA databases primarily consist of genetic information from individuals who have participated in testing. Indigenous populations may have limited access to DNA testing or may choose not to participate, leading to a lack of representation in the databases. As a result, DNA tests may not accurately reflect the ancestral backgrounds of individuals from indigenous populations, highlighting the importance of increasing diversity in genetic databases for more precise ancestry estimates.