transcription

• What is the first step in the transcription process?

  DNA helicase breaks the hydrogen bonds between complementary base pairs in the DNA strand.
• What happens to the DNA strands during transcription?

  The DNA strands separate and unwind, exposing nucleotide bases.
• What pairs with the exposed bases on the DNA template during transcription?

  Free RNA nucleotides pair to the exposed bases on the DNA template.
• What role does RNA polymerase play in transcription?

  RNA polymerase joins the free nucleotides together by phosphodiester bonds to make the mRNA strand.
• What happens to the mRNA strand after it is formed?

  The mRNA strand leaves the nucleus via the nuclear pore and moves to the ribosomes.
• How does RNA polymerase know when to stop adding nucleotides to the mRNA molecule?

  RNA polymerase keeps adding free nucleotides until a stop codon is reached on the DNA strand.
• What is a stop codon?

  A stop codon is a series of three nucleotides on a DNA strand which does not code for an amino acid.
• What are the main steps of transcription?

  1. DNA helicase breaks hydrogen bonds, separating DNA strands.
  2. Exposed nucleotide bases are available for pairing.
  3. Free RNA nucleotides pair with exposed bases.
  4. RNA polymerase forms mRNA by joining nucleotides.
  5. mRNA exits the nucleus and moves to ribosomes.
  6. RNA polymerase continues until a stop codon is reached.
• What is the additional step in eukaryotic transcription?

  Splicing of pre-mRNA
• What are introns?

  Areas of non-coding DNA
• What happens to introns during transcription in eukaryotes?

  They are transcribed into pre-mRNA
• What must occur to pre-mRNA before it can be used by ribosomes?

  It must be spliced to remove non-coding regions
• What are exons?

  Areas of coding DNA
• What is the process of splicing in the context of pre-mRNA?

  • Cutting up the pre-mRNA
  • Removing non-coding regions (introns)
  • Joining together the coding regions (exons)
• Why is splicing important in eukaryotic transcription?

  It ensures that only coding regions are included in mRNA
• What is the final product after splicing pre-mRNA?

  mRNA
• What is the role of ribosomes in relation to mRNA?

  They translate mRNA into proteins