During protein synthesis in eukaryotes, which enzyme is primarily responsible for synthesizing messenger RNA (mRNA) from a DNA template?

• A. DNA polymerase
• B. RNA polymerase II
• C. Reverse transcriptase
• D. Ribosomal RNA

Answer: (B)

Verified step by step guidance

1. Understand the process of transcription: During protein synthesis, transcription is the process where the DNA sequence is copied into mRNA. This occurs in the nucleus of eukaryotic cells.
2. Identify the enzyme responsible for transcription: RNA polymerase is the enzyme that synthesizes RNA from a DNA template during transcription. In eukaryotes, there are three types of RNA polymerases (I, II, and III), each with specific roles.
3. Focus on RNA polymerase II: RNA polymerase II is specifically responsible for synthesizing messenger RNA (mRNA), which carries the genetic code from DNA to the ribosome for translation into proteins.
4. Eliminate incorrect options: DNA polymerase is involved in DNA replication, not RNA synthesis. Reverse transcriptase is used in retroviruses to synthesize DNA from an RNA template, not mRNA synthesis. Ribosomal RNA (rRNA) is synthesized by RNA polymerase I, not RNA polymerase II.
5. Conclude the correct answer: RNA polymerase II is the enzyme primarily responsible for synthesizing mRNA from a DNA template during protein synthesis in eukaryotes.