Suppose you discover a new form of a nucleic acid, XNA. Like DNA, it is double-stranded. You are interested in its mode of replication, so you label parental XNA and then allow that XNA to replicate in the presence of unlabeled bases. After one round of replication, you find the parental XNA intact with both strands labeled and the new XNA with both strands unlabeled. What can you infer?

A) Unlike DNA, XNA replicates conservatively.

B) Like DNA, XNA replicates conservatively.

C) Like DNA, XNA replicates semiconservatively.

D) Unlike DNA, XNA replicates dispersively.

E) Unlike DNA, XNA replicates semiconservatively.

A: Unlike DNA, XNA replicates conservatively

Explanation:

The replication of the DNA is semi conservative. This means that newly replicated double helix DNAs usually consist of one parental strands and one newly synthesized strands. The parental DNA unwinds and each strand serves as template for the synthesis of complementary strands.

In the case of XNA, the two strands of parental XNA were found intact, meaning that the newly produced XNA consist of two newly synthesized strands. This thus means that the replication process is conservative.

Hence, unlike DNA replication that is semi conservative, XNA replication is conservative.