Here's a breakdown of the process:
1. Initiation:
- RNA polymerase, an enzyme, binds to a specific region of the DNA called the promoter. This signals the start of transcription.
- The DNA double helix unwinds, exposing the bases on each strand.
2. Elongation:
- RNA polymerase moves along the DNA template strand, reading the sequence of bases.
- For each base on the DNA, RNA polymerase adds a complementary base to the growing RNA strand.
- The RNA nucleotides are joined together by phosphodiester bonds.
- The RNA strand grows in the 5' to 3' direction.
3. Termination:
- RNA polymerase reaches a specific sequence of bases on the DNA called the terminator.
- The enzyme detaches from the DNA and the newly synthesized RNA molecule is released.
Key differences between DNA and RNA:
* Sugar: DNA contains deoxyribose, while RNA contains ribose.
* Bases: DNA contains thymine (T), while RNA contains uracil (U).
* Structure: DNA is double-stranded, while RNA is usually single-stranded.
Types of RNA produced:
* Messenger RNA (mRNA): Carries the genetic code from DNA to ribosomes, where proteins are synthesized.
* Transfer RNA (tRNA): Delivers amino acids to ribosomes during protein synthesis.
* Ribosomal RNA (rRNA): Forms part of the ribosomes, the site of protein synthesis.
Overall, transcription is a crucial step in gene expression, allowing the genetic information stored in DNA to be accessed and used to produce proteins.
