Updated: 1/20/2022

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  • Overview
    • Process
      • initiation
        • RNAp binds the template DNA strand at the promoter site with the help of transcription factors
      • elongation
        • RNAp synthesizes the mRNA strand in 5' → 3' direction
          • reads template strand in 3' → 5' direction
          • eukaryotic RNAps transcribe introns as well as exons
        • RNAp inhibited by alpha-amanitin (ingestion of the amanita phalloides mushroom)
      • termination
        • prokaryotes
          • two mechanisms
            • rho-dependent
              • rho protein binds the mRNA
              • causes RNAp to fall off
            • rho-independent
              • mRNA has a GC-rich segment that naturally forms a hairpin
              • causes RNAp to fall off
        • eukaryotes
          • transcription continues past the gene and eventually falls off
    • Mono/polycistronic
      • monocistronic = mRNA codes for 1 protein
        • eukaryotes only have monocistronic mRNA
      • polycistronic = mRNA codes for >1 protein
        • e.g. bacterial lac operon
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(M1.BC.15.74) E. coli has the ability to regulate its enzymes to break down various sources of energy when available. It prevents waste by the use of the lac operon, which encodes a polycistronic transcript. At a low concentration of glucose and absence of lactose, which of the following occurs?

QID: 106639

Increased allolactose levels bind to the repressor

6%

(20/354)

Increased cAMP levels result in binding to the catabolite activator protein

47%

(166/354)

Decreased cAMP levels result in poor binding to the catabolite activator protein

29%

(104/354)

Trascription of the lac Z, Y, and A genes increase

4%

(13/354)

Repressor releases from lac operator

11%

(39/354)

M 1 D

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