Transcription and Splicing

• Transcription and splicing occurs in the nucleus
• DNA helicase unwinds a section of DNA to expose the gene that is required for protein synthesis

  • breaks the hydrogen bonds between the bases
• RNA polymerase attaches to the start of one of the newly exposed polynucleotide strands and joins adjacent RNA nucleotides together

  • this forms pre-mRNA which is then spliced to form mRNA
• mRNA diffuses out of the nucleus through a nuclear pore
• After RNA polymerase has detached, the DNA rewinds and forms hydrogen bonds between the complementary bases
• Free RNA nucleotides bind to complementary exposed DNA bases
• Process of transcription and splicing

  1. DNA helicase breaks down hydrogen bonds exposing the template strand
  2. free, activated RNA nucleotides bind to the complementary DNA base
  3. RNA polymerase forms phosphodiester bonds between adjacent nucleotides
  4. splicing removes introns to make mRNA