[Lec 5] Key Terms: Transcription I

Question 1

Key to Transcription for Prokaryotes

Answer 1

1. No primer needed: transcription can start anywhere in the genome
2. RNA not bound to DNA: if RNA always base paired with DNA, protein will never be made and DNA never reannealed.
3. Different parts of the genome can be transcribed to different level: allows cells to specialize

Question 2

Beta and Beta Prime Subunit

Answer 2

required for DNA binding and catalysts

Question 3

Alpha Subunit

Answer 3

Required for DNA binding and assembly

Question 4

Omega Subunit

Answer 4

Stabilizes beta prime binding

Question 5

Sigma Factor

Answer 5

1. can recognize promoters and induce tight binding of the holoenzyme to DNA
2. operates by directing the RNA polymerase to initiate at a specific promoter sequence

Question 6

RNA polymerase core enzyme

Answer 6

can initiate transcript anywhere

Question 7

RNA polymerase holoenzyme

Answer 7

initiate transcription at promoter

Question 8

closed complex

Answer 8

sigma recognizes promoter sequence at -35 and -10 through H-bonding between alpha helix and major groove

Question 9

sigma region 4

Answer 9

binds -35 of promoter and stabilizes interaction

Question 10

sigma region 2

Answer 10

binds -10 of promoter and is important to melting DNA

Question 11

consensus sequence

Answer 11

residues most abundant in position

Question 12

open complex

Answer 12

1. DNA is melted between -11 and +2
2. Does not require energy
3. Involves isomerization of DNA enzyme complex, beta-pincer clamp down on DNA; a portion of alpha factor changes position out of active site

Question 13

Abortive Initiation

Answer 13

1. short RNAs are made and released repeatedly
2. after synthesis of 10+ RNA chain, sigma factor is dissociated

Question 14

pryophosphorolitic editing

Answer 14

addition of PPi nucleotide that was just added

Question 15

hydrolytic editing

Answer 15

polymerase moves back and uses water to cleave off nucleotide

Question 16

Rho-independent

Answer 16

GC rich stem loop followed by run of U’s; DNA encoded

Question 17

Rho-dependent

Answer 17

1. Pause sites->termination sites when “rho” present
2. Termination only occurs when translation stops