What are polymorphisms?

• A. Repeats of amino acids in proteins.
• B. Segments of RNA that regulate translation.
• C. Variations in the DNA sequence among individuals.
• D. A non-coding region.

Answer: (C)

Polymorphisms are variations in the DNA sequence among individuals in a population. These include changes like single-nucleotide differences (SNPs), insertions/deletions, and copy-number variations, and they can occur in either coding or noncoding regions. By definition, a polymorphism is present at a meaningful frequency in the population (often more than about 1%), which distinguishes it from rare mutations. These DNA differences contribute to human diversity and can influence traits, disease risk, or drug response. The other descriptions refer to different concepts: repeats of amino acids describe protein-level makeup, segments of RNA that regulate translation are regulatory RNA elements, and a non-coding region is just a type of DNA region rather than the notion of variation itself.