What best describes a haploid cell?

• A. A cell containing two complete sets of chromosomes (2n).
• B. A cell containing one complete set of chromosomes (n).
• C. A cell with identical sister chromatids attached at centromere.
• D. A cell lacking chromosomes entirely.

Answer: (B)

Ploidy is about how many sets of chromosomes a cell has. A haploid cell contains one complete set of chromosomes, symbolized as n. In humans this means 23 chromosomes, one from each homologous pair, which is the state of gametes like sperm and egg. This contrasts with a diploid cell, which has two complete sets (2n). The fact that a chromosome may be composed of two sister chromatids attached at the centromere describes a replicated chromosome, not the number of chromosome sets; haploid cells can have replicated chromosomes after DNA replication, but the defining feature is having one complete set. A cell lacking chromosomes entirely isn’t the haploid condition. So, the best description is a cell containing one complete set of chromosomes (n).