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Genetics Lecture > Transcription in Prokaryotes > Flashcards

Transcription in Prokaryotes Flashcards

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1
Q

How are base pairs in a gene organized? (?)

A

Every base pair in a gene is numbered

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2
Q

What are the numbers in the transcribed region?

A

the pairs in the transcribed region have positive numbers

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3
Q

What are the numbers in the promoter?

A

have negative numbers

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4
Q

Where is the first base in the promoter?

A

Is the base just before the transcriptional start site.

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5
Q

What does RNA polymerase do?

A

Creates the RNA strand during transcription

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6
Q

What does RNA pol have the ability to do?

A

to separate and unwind the template and coding strands.

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7
Q

What direction does RNA pol move in?

A

3’ to 5’ direction

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8
Q

What is the orientation of the RNA strand synthesized by RNA pol? What does that mean?

A

antiparallel it means it is synthesized 5’ to 3’

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9
Q

What kind of bond can RNA pol form between individual ribonucleotides?

A

phosphodiester bonds

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10
Q

Which end can RNA pol add ribonucleotides to?

A

to the 3’ end

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11
Q

Does RNA pol need a primer?

A

NO

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12
Q

What are the six subunits of E. coli RNA pol?

A

1 and 2. Alpha
3. Beta
4. Beta prime
5. Omega
6. Sigma

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13
Q

Which subunits are found in the core enzyme?

A

beta, beta prime, and the omega

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14
Q

What can the sigma factor do?

A

it has the ability to attach and detach from the other subunits

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15
Q

What is a holoenzyme?

A

it is when the sigma factor is bound to the core enzyme.

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16
Q

What are the three stages of transcription?

A
  1. Initiation
  2. Elongation
  3. Termination
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17
Q

What happens during initiation?

A

All events that are necessary to begin synthesis of the RNA strand

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18
Q

What happens during elongation?

A

It includes most of the events involving transcription synthesis.

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19
Q

What happens during termination?

A

Steps that are required to end termination

20
Q

What are steps in the initiation stage?

A
  1. Attachment of the holoenzyme to the DNA molecule
  2. Attachment to the gene promoter
  3. Separation and unwinding of the template and coding strands
  4. Addition of the first few ribonucleotides to the RNA strand
21
Q

What happens when the holoenzyme encounters a DNA molecule?

A

it attaches to the DNA and then slides along the helix.

22
Q

What happens when the holoenzyme encounters a promoter?

A

it stops and forms a tighter attachment to the DNA at that site

23
Q

What recognizes the promoter sequence in a holoenzyme?

A

Sigma factor

24
Q

What is the function of the promoter with RNA pol?

A

The promoter functions to orient RNA polymerase on the DNA molecule

25
Q

Where does strand separation begin?

A

In the A—T rich region within a promoter

26
Q

What does the holoenzyme do during strand separation?

A

It breaks H bonds in the A—T rich region, separates the template form the coding strand, and unwinds them

27
Q

What is an open complex?

A

The area where the template and coding strand are separated

28
Q

What does the holoenzyme do once the strands are separated?

A

It starts transcription of the new RNA strand

29
Q

Where does the holoenzyme start RNA synthesis?

A

It begins RNA synthesis at the transcriptional start site and adds the first 8-9 ribonucleotides of the new RNA strand

30
Q

When does the sigma factor detach from the core enzyme?

A

The sigma factor detaches once RNA synthesis begins and the first few ribonucleotides of the new RNA strand are added

31
Q

What does the detachment of the sigma factor signify?

A

It marks the end of the initiation stage and the beginning of the elongation stage

32
Q

What occurs during the elongation stage?

A

The remainder of the RNA strand is synthesized

33
Q

What does the core enzyme do during elongation?

A

It moves along the DNA, unwinding the template and coding strands as it moves

34
Q

What happens as RNA pol moves along the template strand?

A

The position of the open complex changes

35
Q

How many base pairs long is the open complex?

A

About 17 base pairs of DNA

36
Q

What is within the open complex?

A

The bases of the RNA strand are H bonded to the bases of the template strand

37
Q

What happens as the template and coding strands are being rewound?

A

Bonded bases within the RNA strand are displaced from the template strand

38
Q

What happens as a consequence as bonded bases in the RNA strand are displaced from the template strand?

A

Only RNA within the open complex is bonded to the template strand

39
Q

When does the termination stage begin?

A

When the core enzyme encounters a terminator within the template strand

40
Q

What does the terminator do?

A

It participates in a process that releases the newly synthesized RNA strand
It also detaches the core enzyme from the template strand

41
Q

What is the attachment of the core enzyme to the template strand dependent on?

A

The pairing between bases in the template and RNA strands within the open complex

42
Q

What happens to the base pairs between the template and RNA strands during termination?

A

The pairing is disrupted
RNA strand and template strand are detached
Core enzyme and DNA are detached

43
Q

What are the different ways RNA synthesis is terminated in E. coli?

A

Rho-dependent
Rho-independent
This is gene specific termination

44
Q

What is Rho-dependent termination?

A

A protein called Rho attaches to the open complex to disrupt H bonds between the RNA and template.
RNA is released and †he core enzyme detaches from DNA

45
Q

What is Rho-independent termination?

A

The protein called Rho is not required.
Sequences within the terminator are sufficient to disrupt bonds between RNA and template strands.
Once RNA is released, RNA pol detaches from DNA

Genetics Lecture (17 decks)

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