Which statement describes a chromosome?

• A. A segment of DNA on a chromosome that codes for a trait
• B. A threadlike, gene-carrying structure found in the nucleus
• C. All the genetic information in an organism
• D. The set of 23 pairs of chromosomes

Answer: (B)

A chromosome is a threadlike, gene-carrying structure found in the nucleus. It consists of DNA wrapped around proteins and becomes visible during cell division, compacting so genetic material can be accurately distributed to new cells. Each chromosome contains many genes and regulatory regions that together carry an organism’s genetic information. Describing a segment of DNA on a chromosome as a chromosome itself confuses a single gene with the entire chromosome, which is why that choice isn’t correct. The idea of all genetic information in an organism refers to the genome, not a single chromosome, and the set of 23 pairs describes the human chromosome complement (karyotype), not an individual chromosome.