Which statement best describes targeted mutation testing?

• A. It tests for a known familial variant.
• B. It sequences the entire genome.
• C. It tests for a known familial variant or a small set of variants when targeted.
• D. It cannot be used when there is a known family variant.

Answer: (C)

Targeted mutation testing focuses on specific genetic changes that are already suspected in a family, rather than scanning the entire genome. When there is a known familial variant, you can design a test to detect that exact change, and if multiple plausible variants exist in that family, you can test a small set of them. This approach is faster and more cost-effective than broad sequencing and is commonly used for testing at‑risk relatives after a pathogenic variant is found in the proband (cascade testing). It is not whole-genome sequencing, which would look across all possible variants. The statement is correct because it captures both the use of testing for a known variant and the possibility of testing a small, targeted set of variants.