Which domain's molecular features are most similar to eukaryotes?

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

Answer: (C)

Archaea share more features with eukaryotes in the molecular machinery that handles gene expression. Their transcription system uses a multi-subunit RNA polymerase and transcription factors that resemble those of eukaryotes far more than the simpler bacterial polymerase and sigma-factor-based regulation. DNA in Archaea is organized with histone-like proteins, giving a chromatin-style packaging similar to what is seen in eukaryotes, whereas bacteria typically lack such histones. The enzymes and factors involved in translation initiation and tRNA processing in Archaea also align more closely with eukaryotic counterparts. All of this makes Archaea more alike to eukaryotes at the molecular level than either bacteria or viruses, which explains why Archaea are the domain whose molecular features most closely resemble those of eukaryotes.