Which domain contains histones?

• A. Archaea
• B. Eubacteria
• C. Eukarya
• D. Viruses

Answer: (A)

Histones are DNA-binding proteins that help package DNA into a compact chromatin structure. In eukaryotes, DNA wraps around histone octamers to form nucleosomes, organizing the genome for regulation and compaction. Archaea also use histone proteins (or histone-like proteins) to package their DNA, though their histones can differ from the eukaryotic ones. Bacteria generally lack histones and rely on other DNA-binding proteins to organize their DNA, and viruses typically do not encode histones for genome packaging.

Given these patterns, Archaea is a domain that contains histone proteins, distinguishing it from bacteria and viruses. (Note that Eukarya also have histones, so histone-based packaging isn’t exclusive to Archaea, but Archaea does have this feature among the listed options.)