The two strands of DNA are separated in transcription by which enzyme?
The correct answer and explanation is:
The enzyme responsible for separating the two strands of DNA during transcription is RNA polymerase.
Transcription is the process by which the information encoded in a segment of DNA is copied into messenger RNA (mRNA). This process is essential for gene expression, as mRNA serves as a template for protein synthesis. RNA polymerase plays a crucial role in initiating and carrying out transcription.
The process begins when RNA polymerase binds to a specific region of the DNA known as the promoter. The enzyme then unwinds the DNA, separating the two strands. This is a critical step because the DNA must be “opened” to expose the template strand, which will be used to synthesize the mRNA. The separation occurs without the need for helicase, the enzyme typically involved in DNA replication. In transcription, RNA polymerase itself possesses helicase-like activity, allowing it to break the hydrogen bonds between complementary base pairs, thereby separating the DNA strands.
Once the DNA is unwound, RNA polymerase moves along the template strand in the 3′ to 5′ direction. As it does so, it synthesizes a complementary mRNA strand in the 5′ to 3′ direction. The mRNA is an exact copy of the DNA sequence, except that thymine (T) is replaced with uracil (U) in RNA. The process continues until RNA polymerase reaches a termination signal, where it detaches from the DNA and releases the newly synthesized mRNA.
Thus, RNA polymerase not only separates the DNA strands but also catalyzes the addition of RNA nucleotides to form the mRNA molecule. It is a multifunctional enzyme essential for the proper flow of genetic information from DNA to RNA.