Transcription is the first step in gene expression, where the genetic information encoded in DNA is copied into a messenger RNA (mRNA) molecule. This mRNA molecule then carries the genetic instructions to the ribosomes, where protein synthesis (translation) takes place.
Here's how it works:
1. Initiation: The enzyme RNA polymerase binds to a specific region of the DNA called the promoter. This marks the beginning of the gene to be transcribed.
2. Elongation: RNA polymerase moves along the DNA strand, unwinding the double helix and using one of the DNA strands as a template to build a complementary mRNA molecule. The RNA polymerase reads the DNA sequence and adds corresponding RNA nucleotides (A, U, G, and C) to the growing mRNA chain.
3. Termination: RNA polymerase reaches a termination signal on the DNA, which signals the end of the gene. The RNA polymerase detaches from the DNA, and the newly synthesized mRNA molecule is released.
Key points:
* DNA and mRNA use different bases: DNA uses thymine (T), while mRNA uses uracil (U). So, in the mRNA molecule, adenine (A) in DNA is replaced by uracil (U) in the mRNA.
* Transcription is essential: It's the process that allows the genetic information stored in DNA to be accessed and used to make proteins.
Let me know if you'd like more details on any of these steps!
