Do bacteria contain introns and histones?

• A. They do not contain introns or histones
• B. They always contain introns and histones
• C. They contain introns but not histones
• D. They contain histones but not introns

Answer: (A)

Bacteria are prokaryotes, so their DNA isn’t packaged into nucleosomes with histone proteins as in eukaryotes. They generally lack introns in their protein-coding genes, and they do not use true histones to organize DNA. Instead, their chromosome is compacted by small DNA-binding proteins such as HU and IHF and other nucleoid-associated proteins. Because introns are uncommon in bacterial genomes and true histones aren’t present, the statement that bacteria do not contain introns or histones captures the typical situation. There are rare exceptions where introns can occur or histone-like proteins exist, but these do not change the overall pattern for most bacteria.