Molecular Biochem

Question 1

What are the different types of RNA?

Answer 1

rRNA= most abundant
mRNA= longest
tRNA= smallest

Rampant, Massive, Tiny

Question 2

Compare prokaryotic vs eukaryotic RNA polymerases

Answer 2

Eukaryotes:
RNA Polymerase I makes rRNA
RNA Polymerase II makes mRNA; opens DNA @ promoter site
RNA Polymerase III makes tRNA

Prokaryotes: 1 RNA polymerase (multisubunit complex) makes all 3 kinds of RNA

Question 3

Alpha-amanitin

Answer 3

Found in death cap mushrooms

Inhibits RNA polymerase II & causes liver failure if ingested

Question 4

Name the start & stop codons

Answer 4

Start: AUG (methionine in eukaryotes, formyl-methionine in prokaryotes)

Stop: UGA, UAA, UAG

Question 5

Origin of replication

Answer 5

Particular sequence in genome where DNA replication begins.

Single in prokaryotes, multiple in eukaryotes

Question 6

Helicase

Answer 6

Unwinds DNA template at replication fork

Question 7

Single-stranded binding proteins

Answer 7

Prevent strands from reannealing

Question 8

DNA topoisomerases

Answer 8

Crease a nick in the helix to relieve supercoils created during replication

*Fluoroquinolones inhibit DNA gyrase (prokaryotic topoisomerase II)

Question 9

Primase

Answer 9

Makes an RNA primer on which DNA polymerase III can initiate replication

Question 10

DNA polymerase III

Answer 10

Prokaryotic only.

Elongates leading strand by adding deoxynucleotides to the 3’ end. Elongates lagging strand until it reaches primer of preceding fragment.

Question 11

Exonuclease

Answer 11

3’-5’ proofreading activity in prokaryotes.
Also excises RNA primer during DNA polymerase I activity.

*Missing from Hepatitis C

Question 12

DNA polymerase I

Answer 12

Prokaryotic only.

Degrades RNA primer and fills in the gap with DNA.

Question 13

DNA ligase

Answer 13

Seals.

Question 14

Telomerase

Answer 14

Enzyme adds DNA to 3’ ends of chromosomes to avoid loss of genetic material with every duplication.

Question 15

Which direction does mRNA reading vs protein synthesis proceed?

Answer 15

mRNA: 5’ –> 3’

Protein synthesis: N to C

Question 16

Shine-Dalgarno sequence

Answer 16

Ribosomal binding site in prokaryotic mRNA upstream from start codon

Helps to recruit ribosome to mRNA

Question 17

Kozak consensus sequence

Answer 17

Occurs on eukaryotic mRNA. Surrounds methionine to serve as initiator for translation.

(gcc)gccRccAUGG [R = adenine or guanine]

Question 18

Capped, tailed, and spliced transcript is called:

Answer 18

mRNA

Question 19

What 3 processing steps occur in the nucleus after transcription?

Answer 19

1. Capping on 5’ end (addition of 7-methylguanosine occurs in cytosol)
2. Polyadenylation on 3’ end (~200 As)
3. Splicing out of introns

Question 20

snRNPs are involved in. . .

Answer 20

splicing of pre-mRNA

Question 21

tRNA has _ _ _ at the 3’ end and binds ___

Answer 21

tRNA has CCA at the 3’ end and covalently binds amino acids