Transcription

What is it?

  • The process of copying the DNA from a gene into mRNA (messenger ribonucleic acid)
  • mRNA is exported into the cytoplasm where it is translated into proteins

Difference between DNA and mRNA

  • mRNA has one strand
  • mRNA replaces thymine (T) with uracil (U)

Three stages of Transcription

  1. Initiation
  2. Elongation
  3. Termination

Initiation

  • Transcription factors bind to a gene
    • Proteins bind to the promoter of a gene
  • Transcription factors allow RNA polymers to bind to the promoter
  • Sometimes Transcription factors block RNA polymerase

Elongation

  • RNA polymerase creates a “transcription bubble” by unwinding and separating DNA strands
  • RNA polymerase adds complementary RNA nucleotides to template strands in 3’ to 5’ direction

Termination

  • Genes have termination sites for stopping transcription

  • Rho dependent

    • Rho protein causes termination

  • Rho-independent

    • Formation of a hairpin loop structure causes termination