Answer:
The fact that DNA replication and gene expression in archaea more closely resemble eukaryotic cells than the same processes in bacteria, despite both archaea and bacteria being prokaryotic, suggests that there are significant differences between the two domains of prokaryotes in terms of their cellular machinery and molecular processes.
Although archaea and bacteria are both classified as prokaryotes because they lack a nucleus and other membrane-bound organelles, they differ in several key ways. For example, archaea have a distinct cell membrane composition that is more similar to that of eukaryotes than to bacteria. Additionally, archaea have a more complex transcriptional machinery, with RNA polymerases that more closely resemble those found in eukaryotes.
These differences in cellular machinery likely arose through evolutionary divergence, with archaea and eukaryotes sharing a common ancestor that was distinct from the ancestor of bacteria. Therefore, the similarities between archaea and eukaryotes in terms of DNA replication and gene expression suggest that these processes were already complex and well-developed in the common ancestor of archaea and eukaryotes, and were later lost or simplified in bacteria.