A researcher introduces a signal produced by bacteria to eukaryotic cells that she is culturing in the laboratory. Remarkably, she notices that this signal results in an increase in eukaryotic gene expression. How is this possible?

A. This gene expression is likely independent of the presence of the prokaryotic signal.

B. The signal is either similar in structure to a ligand used by eukaryotes, or this signaling pathway is utilized by both prokaryotes and eukaryotes.

C. This signaling pathway might actually be utilized by both prokaryotes and eukaryotes.

D. This signal is likely similar in structure to ligands utilized by eukaryotic cells.

E. This prokaryotic signal likely travels directly into eukaryotic cells and acts as a transcription factor.

Answer:B. The signal is either similar in structure to a ligand used by eukaryotes, or this signaling pathway is utilized by both prokaryotes and eukaryotes.

Explanation: Eucaryotic cell is a cell whose Nucleus is clearly defined and confined within a membrane.

Procaryotic cell is a cell which does not have a clearly defined Nucleus.

Signals are stimuli which can be felt by an organism, specific organismal have its own kinds of signals which it can respond to, but some times signals with specific features can create response in two or more type or species of organisms. What happened in the lab is a case where a partial signal can be sensed by both procaryotes and eucaryotes because it has either a similar structure or its pathway can be used by either Eucaryotic cells and procaryotic cells.