Question

A cell has a circular chromosome and histone proteins associated with its DNA, but lacks a nuclear membrane. Choose the domain of the cell with the best justification.

A. The cell belongs to Archaea because it has histone proteins, which are present in Archaea and Eubacteria but absent in Eukaryota.
B. The cell belongs to Eukaryota because it has a circular chromosome, which is present in Eukaryota and Eubacteria but absent in Archaea.
C. The cell belongs to Eubacteria because it has histone proteins, which are present in Eubacteria and Eukaryota but absent in Archaea.
D. The cell belongs to Archaea because it has histone proteins, which are present in Archaea and Eukaryota but absent in Eubacteria.
E. The cell belongs to Eubacteria because it lacks a nuclear membrane, which is present in Eukaryota but absent in Eubacteria and Archaea.

Answer 1

The correct answer is: D. The cell belongs to Archaea because it has histone proteins, which are present in Archaea and Eukaryota but absent in Eubacteria.

Step-by-step explanation:

A cell with a circular chromosome and histone proteins associated with its DNA but lacking a nuclear membrane can only belong to the Archaea domain.

Archaea is the domain of ancient bacteria - they have similarities with both Eukaryotes and Eubacteria.

Archaea and Eukaryotes both have DNA associated with histone proteins, but eukaryotes have multiple linear chromosomes, not just a circular one; besides, eukaryotes have a nuclear membrane while archaea do not. On the other hand, Archaea and Eubacteria both have one circular chromosome, but eubacteria don't have their DNA associated with histones.

For these reasons, the cell described is definitely in the Archaea domain.