Transcription

Question 1

4 RNA molecules

Answer 1

mRNA - amino acid, transcripts of genes
tRNA - Bring AA to the ribosome
rRNA - form ribosome
snRNA - RNA processing, slicing and gene regulation in eukaryotes

Question 2

RNA Polymerase (prokaryotes)

Answer 2

core polymerase - helicase & nucleotidyl transferase activity
sigma factor - promoter recognition

Question 3

Regions of a prokaryotic gene

Answer 3

promoter
RNA coding sequence
Terminator

Question 4

Prokaryote Promoter

Answer 4

-35 TTGACA, -10 TATAAT (variations can alter the binding ability of RNA polymerase –> rate of transcription)

Question 5

Rifampin

Answer 5

Antibiotic from Streptomycin for TB
Inhibits initiationof transcription
blocks first phosphodiester bond - binder to RNA polymerase.
Mutations in gene for RNA pol and topoisomerase could lead to drug resistance

Question 6

Eukaryotic Promoters

Answer 6

conserved short sequence near transcription start:
GC box (GGGCGG), TATA box (TATAAA), CAAT box (CCAAT)

Question 7

Proteins of Eukaryote Transcription:

Basal Transcription Machinery

Answer 7

TATA box binding protein
TFIIA
TFIID
TFIIB
TFIIH
TFIIE

Question 8

TATA box binding protein (TBP)

Answer 8

eukaryotes

subunit of TFIID

Question 9

TFIID

Answer 9

distortion in DNA helix allowing the recruitment of other transcription factors

Question 10

TFIIA & TFIIB

Answer 10

involved in RNA polymerase interactions

start site recognition

Question 11

TFIIH

Answer 11

Contains a DNA helicase to unwind DNA.

Activates RNA polymerase by phosphorylation

Question 12

TFIIE

Answer 12

Involved in positioning RNA polymerase

Question 13

Enhancer

Answer 13

May be anywhere in the DNA with relation to the promoter.
DNA bends to allow for binding via an activator –> stimulation of transcription.
Presence allows increased levels or tissue specific transcription.

Question 14

Amanita phalloides

Answer 14

alpha-amanitin toxin
RNA polymerase II inhibitor
4 clinical phases:
1. asymptomatic
2. GI phase - intestines can’t make proteins
3. apparent recovery - few Sx
4. Hepatic phase - toxins migrate through circulation

TX: GI decontamination. High does PCN - inhibits activity in the liver. Liver transplant

Question 15

Courmarins - novobiocin

Quinolones - nalidixic acid & ciproflaxacin

Answer 15

inhibit Bacterial gyrase

build up of -ve supercoils

Question 16

Intrinsic Termination Sequence - Rho IN-dependent

Answer 16

GC rich segments followed by a U run that form stem loop structure in the transcribed RNA –> stearic hindrance and release from the DNA.

Question 17

Extrinsic Termination - Rho DEpendent

Answer 17

Rho factor attaches to RNA transcript at c-rich recognition site and follows the RNA polymerase. When RNA Pol reaches the termination sequence it stops. Rho catches up, unwinds the hybrid strand (helices activity) and all parties dissociate.

Question 18

Actinomycin D

Answer 18

equal opportunity DNA binding and inhibition of transcription/translatiion of pro/eukaryotes.

Anti-cancer.

Question 19

Prokaryotic Promoter sequences

Answer 19

-35 TTGACA & -10 TATAAT(Pribnow) bp from transcription start.

Question 20

RNA Polymerase

eukaryotes

Answer 20

1 - rRNA
2 - mRNA, snRNA, miRNA
3 - tRNA, snRNA

Question 21

UTR

Answer 21

untranslated trailer sequence

Question 22

Post Transcriptional Modification - Eukaryotes

Answer 22

Addition of a 5’ cap structure
Addition of a 3’ poly-A tail
Removal of introns by RNA splicing
Translation of mRNA by the ribosome