Copy number variants in germline testing refer to what?

• A. Duplications or deletions of DNA segments that can cause disease.
• B. Single base substitutions.
• C. Epigenetic modifications.
• D. Balanced translocations.

Answer: (A)

Copy number variants are changes in the number of copies of DNA segments, typically deletions or duplications, that can be present in the germline and contribute to disease. In germline testing, this means looking for pieces of the genome that are missing or present in extra copies compared with a reference. This is what makes the option describing duplications or deletions of DNA segments the correct choice. By contrast, single base substitutions are small nucleotide changes, epigenetic modifications alter gene expression without changing the DNA sequence, and balanced translocations rearrange material without changing the overall copy number. CNVs can disrupt dosage-sensitive genes and lead to developmental or inherited disorders, and are often detected by chromosomal microarray or similar copy-number analysis methods.