Transcription, the first step in protein synthesis, involves the binding of RNA polymerase to the promoter region of DNA to unwind the double helix and synthesize a complementary mRNA strand, which continues until reaching a terminator signal, followed by processing in eukaryotes that adds a 5' cap, a poly-A tail, and splices out introns before the mRNA exits the nucleus and enters the cytoplasm for translation.
The first step in protein synthesis is transcription. During transcription, the DNA serves as a template to create a complementary RNA strand. Here’s a brief overview of the process:
1. **Unwinding the DNA**: The enzyme RNA polymerase binds to a specific region of the DNA (the promoter region) and unwinds the double helix, exposing the nucleotide sequences of the gene that will be transcribed.
2. **Synthesis of RNA**: RNA polymerase then synthesizes a single strand of messenger RNA (mRNA) by adding RNA nucleotides that are complementary to the DNA template strand. For example, where the DNA has an adenine (A), the RNA will incorporate a uracil (U) instead of thymine (T).
3. **Termination**: Transcription continues until RNA polymerase reaches a terminator signal, indicating that the gene has been fully transcribed. The newly formed mRNA strand is then released.
4. **Processing**: In eukaryotes, the primary mRNA transcript undergoes processing, which includes the addition of a 5' cap, a poly-A tail, and splicing to remove introns (non-coding regions).
Once transcription is complete, the mRNA exits the nucleus (in eukaryotic cells) and enters the cytoplasm, where it can be translated into a protein during the next phase of protein synthesis, known as translation.
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