19. Transcription and translation worked examples

Question 1

what is the process of transcription?

Answer 1

• RNA pol.
  – recognises -35 and -10 sites
• binds at -10
  – inwinds DNA (easy because AT rich)
• first mRNA inserted at +1 position
• RNA pol inserts bp fro 5’-3’
  – complementary base pairing with template strand
• termination sequence
  – tells RNA pol to stop
  – GC rich area in RNA sequence which is self-complimantary

Question 2

how does the termination sequence work?

Answer 2

• GC rich area on RNA sequence
• self-complementary
  – fold back on itself making hair pin (stalls RNA pol)
• hairpin followed by stretch of U’s in RNA
  – match up with A’s in template DNA
  – forms weak interaction with template DNA
  – with stalled polymerase, enzyme fall off and liberate new RNA transcript

Question 3

what is the mRNA transcript?

Answer 3

• from +1 to terminator region
  – contains 5’-3’ untranslated regions (UTR)
• up and down stream of start codons

Question 4

**-

Answer 4

-