What is a founder variant, and why does it matter for population-specific carrier screening?

• A. A variant unique to a single family that is not seen in the population.
• B. A sequencing artifact.
• C. A common benign variant.
• D. A pathogenic variant with high frequency in a population due to founder effect.

Answer: (D)

A founder variant is a genetic change that originated in a single ancestor and, because of how populations grew and spread, appears at a higher frequency in a particular group. If that change disrupts gene function and causes disease, people in that population are more likely to carry it. That makes population-specific carrier screening more efficient: tests can be tailored to include these high-frequency, disease-causing variants, capturing a larger portion of carriers within that ancestry than a generic panel would. This is why the correct description emphasizes a pathogenic variant with increased population frequency due to the founder effect. The other options don’t fit: a private family variant doesn’t spread through the population; a sequencing artifact isn’t a real variant; a common benign variant could be frequent but isn’t defined by a founder-driven rise in frequency linked to disease risk.