chapter 5

Question 1

Types of RNA during transcription

Answer 1

-mRNA: messenger RNA. “gene” code for protein, produced by RNA polymerase (1000-3000)
-tRNA: transfer RNA (91 bases long), folded like a cloverleaf, transfer aa to protein. produced by RNA poly III.
-rRNA: ribosomal RNA: 28s-18s, produced by poly III; embedded in ribosomes
-SnRNA: small nuclear RNA; stay in nucleus, involved in RNA processing, produced by poly III
-miRNA: microinterefence RNA, involved in gene regulation. (21 bases)

Question 2

what are core promotors in intitiation of transcription

Answer 2

starting site for RNA synthesis
-includes INr and TATA box

Question 3

Inr

Answer 3

spans transcription start site

Question 4

TATA box

Answer 4

located at -30: TATAAA

Question 5

transcription can occur with ______ at a low level

Answer 5

Inr and TATA box

Question 6

promotor proximal elements

Answer 6

determine the efficiency of promotor
-CAAT: (-75)
-GC box: (-90)

Question 7

proteins in the initiation of transcription

Answer 7

-transcription factor proteins
TFIID: binds to TATA box first
TFIIA: rely on TFIID to bind on TATA; joins underneath
TFIIB: joins CAT, relies on TFIID
TFIIF: associated with RNA poly II
TFIIH and TFIIE: break H bonds in DNA around TATA= make bubble

Question 8

what are the transcription steps and where do they occur?

Answer 8

1.intitiation
2. elongation
3. termination
- inside the nucleus

Question 9

what happens to the transcription factor proteins in elongation

Answer 9

-all fall off

Question 10

transcription elongation only needs _______

Answer 10

RNA polymerase
-it has its own helicase activity
-no sSB

Question 11

describe the process and structure during elongation

Answer 11

-small bubble around poly II
-winds back up as it moves forward
-leaves no large replication bubbles
-no proofreading

Question 12

RNA proofreading

Answer 12

-RNA poly II
-5-3 polymerase
-no proofreading
-no exonuclease activity

Question 13

DNA proofreading

Answer 13

DNA polymerase II
-5-3 polymerase
-3-5 exonuclease activity
-5-3 exonuclease activity (removal of primers).

Question 14

transcription termination can be

Answer 14

-Rho dependent protein: binds to polymerase and falls off
-Rho independent: folds in itself, whips poly away and falls off.

Question 15

introns

Answer 15

removed, dont code for protein

Question 16

exon

Answer 16

kept to code for protein

Question 17

what is the purpose of RNA processing and where does it occur?

Answer 17

produces mature mRNA, in the nucleus

Question 18

what are the 3 steps in RNA processing?

Answer 18

-capping
-3’ polyadenylation
-RNA splicing

Question 19

capping process

Answer 19

-occurs on the 5’ end
- capping enzyme: adds guanine nucleotide
-purpose: aids in degradation protection and important for the binding of the ribosome in the initial step of translation

Question 20

3’ polyadenylation process

Answer 20

-poly A polymerase: adds about 200 A’s to 3’ end
-polyadenylation protein: stick to single-stranded RNA (during transcription). cuts RNA molecule then adds A’s

Question 21

poly-A tail

Answer 21

-50-250 adenine
-purpose: buy time for more protein to produce
-only relative for the same gene, different tail.

Question 22

RNA splicing removes ______

Answer 22

introns

Question 23

describe the components of RNA splicing

Answer 23

SnRNA+ proteins form snURPS
-U1
-U2
-U4
-U5
-U6
-cut introns and splice exons together

Question 24

describe the RNA splicing process

Answer 24

1. U1 binds GU
2. U2 binds from brand point
3. U4/U6 and U5 bind to U1 and U2= loop
4. U4 exits= exons together
5. splicing= mature mRNA