Transcription

• Promoter region

  Signals to RNA polymerase to bind an begin transcription of a specific gene

  Antisense strand is used as the template for RNA polymerase to build the complimentary RNA from
• transcription

  1. RNA polymerase hydrolyses hydrogen bonds between nitrogenous bases to access the single stranded anti-sense strand
  2. the antisense strand is read in the 3-5 prime direction and the complimentary mRNA strand is built in the 5-3 prime direction to due the antiparallel.
  3. when complimentary nucleotides aer recruited, RNA pol reforms the hydrogen bonds and reforms double helix
  4. eventually RNA polymerase t o reaches a terminator sequence stopping transcription and releasing a pre-mRNA transcript
• RNA polymerase

  adds nucleoside triphosphate to the enlarging mRNA molecule. As the triphosphate are added, two phosphates are released producing RNA nucleotides. these molecules are added in the 3 prime direction end of the growing mRNA strand
• post transcriptional modification

  1. pre mRNA is fitted with a 5 prime guanine cap and a 3 prime poly-adenine cap. acts as a protective measure against mRNA transcript degradation as it travels to ribosomes to maintain integrity of coding region
  2. spliceosomes remove non-coding introns, exons can rearrange resulting in increased variation of proteins
  3. variation of proteins can also be formed by alternating spliceosomes of exons
  4. once exons join the mature mRNA transcript can lead the nucleus and travel to a ribosome
• highly repetitive sequences STR’s (short tandem repeats)

  individuals have different numbers of repeats in their intron STR’s this can create a unique DNA finger print
• telomeres

  contain non-coding introns - highly repetitive protect against mistakes and wear and tear occurring during DNA replication