Which of the following is the best evidence for a three- domain system?
A) There are three distinctly different types of nuclei.
B) Some bacteria live in extreme environments.
C) There are three distinctly different Gram reactions.
D) There are three distinctly different sets of metabolic reactions.
E) Nucleotide sequences in ribosomal RNA vary between all three domains.

Question

Quizplus · Accepted Answer

The nucleotide sequences in ribosomal RNA vary between all three domains, providing strong evidence for the three-domain system. This molecular evidence suggests that the three main groups of organisms (Archaea, Bacteria, and Eukarya) diverged from a common ancestor over 3 billion years ago, and have since evolved distinctive characteristics that classify them into three separate domains. While the other choices provide supporting evidence for the three-domain system, they are not as strong as the molecular evidence.

Which of the Following Is the Best Evidence for a Three-