Biochemistry - Ch 26 - Rna Metabolism

Front 1

All RNA is synthesized on a template of _____.

Back 1

...DNA.

Front 2

What were the 3 types of RNA we studied?

(abbreviation and name)

Back 2

rRNA = Ribosomal RNA

tRNA = Transfer RNA

mRNA = Messenger RNA

Front 3

2 synonymous terms for the "template" DNA strand are:

Back 3

1) antisense

2) non-coding

Front 4

2 synonymous terms for the "non-template" DNA strand are:

Back 4

1) sense

2) coding

Front 5

2 synonymous terms for the "antisense" DNA strand are:

Back 5

1) template strand

2) non-coding

Front 6

2 synonymous terms for the "non-coding" DNA strand are:

Back 6

1) antisense

2) template strand

Front 7

2 synonymous terms for the "sense" DNA strand are:

Back 7

1) coding

2) non-template

Front 8

2 synonymous terms for the "coding" DNA strand are:

Back 8

1) sense

2) non-template

Front 9

The E. coli RNAp holoenzyme is labeled with the subunit composition:

Back 9

α₂ββ'ωσ

Front 10

The E. coli RNAp core enzyme is labeled with the subunit composition:

Back 10

α₂ββ'ω

Front 11

DNA sequences that signal transcriptional start sites are called...

Back 11

...promoters.

Front 12

By convention, promoter sequences show the (non-sense/sense) strand.

Back 12

...sense...

Front 13

Sequence of Sense strand for promoters:

The Initiation site is labeled with the number _____.

Back 13

+1

Front 14

Sequence of Sense strand for promoters:

The type of nucleotide that is found at the Initiation site is usually...

Back 14

...purine. (A or G)

Front 15

Sequence of Sense strand for promoters:

The Pribnow Box is represented by the conserved nucleotide sequence...

Back 15

...TATAAT

Front 16

Sequence of Sense strand for promoters:

The Pribnow Box is labeled with the number _____.

Back 16

-10

Front 17

Describe the process of the E. coli RNAp holoenzyme recognizing and attaching to DNA.

(5 steps)

Back 17

1) σ recognizes the promoter

2) Holoenzyme (α₂ββ'ωσ) loosely associates with DNA

3) Moves along until it finds promoter sequence

4) Opens up DNA

5) Initiates transcription and loses σ

Front 18

What are 2 common features that termination sequences of many E. coli genes share?

Back 18

1) A series of 4-10 consecutive A-T base pairs.
- A's are on the *template* strand.

2) G + C rich sequence that immediately precedes the series of A-T's.

Front 19

The transcription of a termination sequence forms what type of structure?

Back 19

stem-loop

Front 20

What are the 2 methods by which transcription can be terminated?

Describe each briefly.

Back 20

1) Termination sequence
- stem-loop slows down RNAp
- weak base pairing
- rewinding DNA pushes RNA off the template

2) Rho-factor dependent termination
- rho protein
- recognizes sequence on nascent RNA
- unwinds the RNA-DNA complex

Front 21

True/False:

Once eukaryotic DNA is transcribed to form a strand of mRNA, the mRNA can be used immediately as a template to synthesize proteins.

Back 21

FALSE.

The mRNA of eukaryotes has to undergo post-transcriptional processing before it can be used.

Front 22

The 3 main types of processing the eukaryotic mRNA undergoes are:

Back 22

1) 5' capping

2) Polyadenylation (i.e. poly-A tail)

3) Splicing

Front 23

Post-transcriptional modification of mRNA:

Describe the "5' cap" and how it is linked.

Back 23

A structure consisting of a 7-methylguanosine (m⁷G) residue joined to the transcripts initial (5') nucleotide via a 5'-5' triphosphate bridge.

Front 24

Post-transcriptional modification of mRNA:

Describe the 3 steps involved in "capping"

Back 24

1) Removal of the 5' phosphate

2) Addition of guanine mono-phosphate.

3) Methylation of guanine at N7.

Front 25

Post-transcriptional modification of mRNA:

Describe the 2 step process of "poly-A addition".

Back 25

1) Cleavage of 15-25 nucleotides 3' to AAUAAA sequence

2) Template independent addition of ~250 A to 3' end of RNA

Front 26

Post-transcriptional modification of mRNA:

What is the function(s) of the "poly-A tail"?

Back 26

Gives stability.

Acts as a timer for degredation.

Front 27

Post-transcriptional modification of mRNA:

What happen during splicing?

Back 27

Splicing is the removal of non-coding sequences of mRNA.

The introns (non-coding regions) are removed and the exons (coding regions) are spliced together.

Front 28

Post-transcriptional modification of mRNA:

Which are bigger, introns or exons?

Back 28

Introns are around ~4-6 times larger than exons.

Front 29

Post-transcriptional modification of mRNA:

preRNA (RNA that has yet to be modified) is also known as what?

Back 29

heterogeneous nuclear RNA (hnRNA)

Front 30

True/False:

hnRNA can be used to synthesize proteins!

Back 30

FALSE

hnRNA has not yet been processed.