Chaper 3: Transcription and RNA Processing

Question 1

Name two drugs that can inhibit prokaryotic RNA polymerase.

Answer 1

rifampin, Actinomycin D
(Actinomycin D can inhibit both prokaryotic & Eukaryotic polymerase)

Question 2

What does RNA polymerase 1, 2, 3 each synthesize?

Answer 2

RNAP 1: rRNA
RNAP 2: mRNA
RNAP 3: tRNA

Question 3

Name two chemicals that can inhibit Eukaryotic RNA polymerase 2.

Answer 3

Actinomycin D & alpha-amanitin(mushrooms)

Question 4

Three steps of Processing in Eukaryotic Pre-Mesenger RNA?

Answer 4

1. 7-methylguanosine cap is added to the 5’ end
   - Serves as ribisome-binding site & helps to protect the mRNA chain from degardation.
2. Poly-A tail is attached to the 3’ end.
   - Protects the message againt rapid degradation and aids in its transport to the cytoplasm.
3. Introns are removed from hnRNA by splicing.

Question 5

Every Eukaryote’s trascription is a polycistronic message (O/X)

Answer 5

X. Every Eukaryote’s transcription is a monocistronic message

Question 6

What is Alternative splicing? And give me some examples.

Answer 6

For some genes, the primary transcript is spliced differently to produce two or more variants of a protein from the same gene.
ex) Tropomyosin & Troponin T in muscles, unstimulated B lymphocytes

Question 7

Tell me the size of Ribisome on Prokaryotic & Eukaryotic cells.

Answer 7

Prokaryotic Ribosome: 30S + 50S = 70S
Eukaryotic Ribosome: 40S + 60S = 80S

Question 8

What is the function of Shiga toxin(Shigella dysenteriae) and Verotoxin; Shiga-like toxin(enterohemorrhagic E. coli)?

Answer 8

halt’s protein synthesis.
- inactivate the 28S rRNA in the 60S subunit of the eukaryotic ribosome. They are RNA glycosylases that remove a single adenine residue from the 28S rRNA.

Question 9

What is RNA editing, and any examples in human?

Answer 9

It is a process by which some cells make discrete changes changes to specific nucleotide sequences within a RNA molecule after its gene has been transcribed by RNA polymerase.
- Cytosine-to-Uracil deamination in the apoprotein B gene. Apoprotein B100 is expressed in the liver, and apoprotein B48 is expressed in the instestines. In the intestines, the mRNA is edited from a CAA sequence to be UAA, a stop codon, thus producing the shorter apoprotein B48 form.