Basic Transcription Part 1 Flashcards Preview

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Flashcards in Basic Transcription Part 1 Deck (38):
1

three steps in transcription

- initiation - rate-limiting
- elongation
- termination

2

differential gene expression

- all cells in your body have the same DNA but what makes cells unique are the genes that are expressed in them

3

transcription of genes

- one part of more general term of gene expression

4

Coding Strand

- sequence that resembles mRNA

5

Template Strand

- make transcript
- read by RNA pol

6

RNA transcription requires

- RNA polymerase enzymes
- promoter sequence on the DNA template
- ribonucleotides

7

holoenzyme

- entire enzyme
- core + sigma factor

8

core

- all but sigma factor
- Beta and Beta'
- alpha

9

sigma factor

- specificity factor
- directs the polymerase to initiate transcription at specific promoters

10

sigma promotes what type of binding

- tight binding between RNA pol and promoters

11

results of filter binding assay

- holoenzyme dissociates with a half time of 30-60 hours
- core dissociates with a half time of less than 1 minute
- holoenzyme binds tightly

12

holoenzyme binding to promoters

- tight because of sigma subunit

13

holoenzyme binding to DNA

- loose

14

+1

- first nucleotide incorporated into RNA

15

adding a nucleotide to RNA

- nucleic acids always added to 3' OH
- attack of old 3' OH to new 5' PO4

16

attack of old 3' OH to new 5' PO4

- release of pyrophosphate and formation of phosphodiester linkage

17

Does RNA polymerase require a primer

- No

18

Does DNA polymerase require a primer

- 3' OH primer

19

Promoters

- DNA sequences where RNA polymerases bind to initiate transcription
- Major points of control of gene regulation

20

Prokaryotic RNA polymerases

- have the intrinsic capacity to recognize promoters

21

Eukaryotic RNA polymerases

- do not have the intrinsic capacity to recognize promoters
- need a number of other protein factors to bind near promoters to recruit RNA pol

22

(-)10 and (-)35 sequences

- sequences are recognized and bound by sigma subunit of RNA pol
- space needed for RNA pol to bind

23

prokaryotic promoter composed of

- upstream element
- Fis sites
- core promoter

24

upstream element

- promotes high levels of transcription
- stabilize interaction with pol and core promoter

25

nucleotides upstream of the +1

- are not transcribed.

26

regions of the sigma factor

- regions 1-4

27

region 1

- found only in primary sigma factor (found in all cells all the time)
- prevents sigma from binding DNA by itself

28

region 2

- most highly conserved
- binds core
- promoter recognition at -10

29

region 3

- helix-turn-helix core and DNA binding

30

region 4

- promoter recognition of -35 box

31

regions of sigma region 2

- Regions 2.1
- Regions 2.4

32

Regions 2.1

- binds core
- amino terminus

33

Regions 2.4

- promoter recognition at -10 box

34

sigma cycle

- binds to RNA pol
- transcribes DNA
- falls off
- recycled again

35

terminators

- at end of gene cause polymerase to fall off template releasing template

36

two types of terminators

- intrinsic terminators - requires no proteins
- RNA dependent terminators - requires Rho

37

intrinsic termination process

- hairpin begins to form due to string of Ts
- hairpin destabilizes the RNA-DNA hybrid which helps keep RNA pol on DNA
- transcript falls out
- polymerase falls off

38

rho dependent termination

- requires hairpin loop but no string of T's
- Rho binds to transcript at rho loading site and pursues polymerase
- hairpin forms, polymerase pauses, rho catches up
- rho helicase releases transcript by unwinding DNA-RNA hybrid
- causes termination