Which molecule carries genetic information across the nuclear membrane to direct protein assembly?

• A. mRNA
• B. DNA
• C. Protein
• D. Lipids

Answer: (A)

Genetic information flows from DNA to protein through RNA, with messenger RNA serving as the courier that exits the nucleus and directs protein assembly. Messenger RNA is made in the nucleus as a copy of the gene (transcription) and then travels through nuclear pores into the cytoplasm, where ribosomes read its codons and synthesize the corresponding polypeptide. DNA sits inside the nucleus and does not cross the nuclear membrane, and proteins or lipids do not carry the genetic code between compartments. Therefore, the messenger RNA is the molecule that carries genetic information across the nuclear membrane to direct protein synthesis.