n what direction is the RNA strand synthesized by RNA Polymerase II? 5' to 3' 3' to 3' 3' to 5' 5' to 5' Depends on the cell type

Direction of RNA Synthesis

RNA Polymerase II synthesizes RNA in the 5' to 3' direction. This means that as the enzyme catalyzes the addition of ribonucleotides to the growing RNA strand, it adds nucleotides to the 3' end of the chain. This process reflects the antiparallel nature of nucleic acids, where the DNA template strand runs in the opposite direction (3' to 5') relative to the direction of RNA synthesis.

Explanation

1. Template Strand Orientation: RNA Polymerase II uses one of the DNA strands as a template for synthesis. If the DNA template is oriented 3' to 5', this allows the RNA strand, being synthesized, to grow in the 5' to 3' direction.

2. Nucleotide Addition: During the elongation process, nucleotides are added to the 3' hydroxyl (OH) group of the last nucleotide in the RNA chain. The incoming ribonucleoside triphosphates (NTPs) undergo a condensation reaction, releasing pyrophosphate and forming a phosphodiester bond.

3. Significance: The 5' to 3' orientation is critical in various biological processes, including transcription initiation, elongation, and termination, as well as in the translation of mRNA.

Thus, the final answer to the question is:

Final Answer

5' to 3'