BIOL 310 - Ch 13 Lecture Notes

  • transcription

    • making RNA from a DNA template

    • RNA

      • 2’ hydroxyl group

      • single stranded

      • uracil instead of thymine

      • complementary to template DNA

      • homologous to coding DNA

  • RNA structure

    • primary structure - linear & single stranded

    • secondary structure - can form stem-loop regions

  • types of RNA

  • transcription

    • RNA is transcribed from (complementary to) the template strand

    • identical to the coding strand (with U not T)

  • transcription regulation

    • strands that runs 5’ → 3’ is non template strand (coding)

    • complementary strand is template strand (noncoding)

    • chemically attract RNA polymerase

      • consensus sequence at -35 and -10

        • severe mutations could mean that elimination of theses sequences would lead to elimination of that particular gene

      • G or C at +1 preferred

    • transcription bubble - there is no big replication fork

      • RNA will look like the coding except it uses uracil

  • transcription process

    • promoter- sequence that recruits polymerase

    • consensus seq

      • some species do have TATAAA (can differ among species)

      • there can be variety in sequences

    • core RNA promoter & sigma factor come together at the promoter

    • holoenzyme - group of enzymes working together to achieve a function; initiates transcription

    • adding the first base is a tenuous process since it is RNA being synthesized without a primer

      • the three hydrogen bonds of C & G

    • termination

      • Rho independent

        • inverted repeated sequence in coding strand are followed by an AT rich sequence

        • makes the polymerase slow down — when the uracil is being added the GC rich regions make the polymerase fall off during hairpin loop formation

      • Rho dependent

        • protein is made up of six copies of a subunit protein

        • protein made up of 6 copies of subunit that has a gate which rho attaches to

          shuts the gate & twirls around

          hairpin still forms

          AT rich region present

          rho catches up to polymerase & falls off by either pushing, pulling, or colliding

        • hairpin formations aren’t as strong compared to the independent termination

          • hypothesized that is it either pulled, pushes or collides to remove itself from the template

  • transcription in eukaryotes

    • has a more complex process

    • still has core RNA polymerase & sigma factor