Biochem Exam 4 Clicker Flashcards
A nucleotide contains which of the following:
a. 6 - carbon sugar
b. at least 3 phosphate groups
c. nitrogenous sugar
d. 4 - carbon sugar
e. nitrogenous base
NITROGENOUS BASE!
The first committed step in pyrimidine biosynthesis is:
a. The action of CPS2 to create IMP
b. The action of ribonucleotide reductase to create dTTP
c. The action of CPS2 to create carbomoyl phosphate
d. The action of Glutamine: PRPP Aminotransferase
THE ACTION OF CPS2 TO CREATE CARBOMOYL PHOSPHATE
The difference between ribose and deoxyribose is:
a. Ribose is a 6 carbon sugar and deoxyribose is a 5
b. At the 2’ carbon position
c. Deoxyribose has more hydrogens
d. Ribose has one nitrogenous base and deoxyribose has two
AT THE 2’ CARBON POSITION
Nucleotides are joined together in a polymer chain via a:
a. Glycosidic Bond
b. Phosphodiester Bond
c. DNA Ligation
d. Hydrogen Bond
e. Nucleophilic Reaction
PHOSPHODIESTER BOND
If a DNA sequence is comprised of 20% adenine, what percent of the sequence is guanine?
30%
Which of the following best defines the nucleosome core particle?
a. Histone octamer + DNA + histone H1
b. Histone octamer + linker DNA
c. Histone octamer + DNA wrapped around octamer
d. Histone octamer + DNA + histone H1 + linker DNA
HISTONE OCTAMER + DNA WRAPPED AROUND OCTAMER
Which is FALSE about DNA polymerase 3?
a. Requires a template strand for synthesis
b. Can use mono, di, and triphosphate nucleotides in synthesis
c. Has polymerase and exonuclease activity
d. Requires a primer - can only addd nucleotides to a growing chain
e. Uses magnesium to stabilize its active site
CAN USE MONO, DI, AND TRIPHOSPHATE NUCLEOTIDES IN SYNTHESIS
What best describes chain elongation during replication?
a. The nucleotide diphosphate is attached to the 5’ hydroxyl of the new strand
b. The nucleotide monophosphate is attached to the 5’ hydroxyl of the new strand
c. The nucleotide triphosphate is attached to the 3’ - hydroxyl of the new strand
d. The nucleotide triphosphate is attached at the 3’ hydroxyl of the template strand
THE NUCLEOTIDE TRIPHOSPHATE IS ATTACHED AT THE 3’ - HYDROXYL OF THE NEW STRAND
Which of these proteins acts ahead of the replisome to ensure efficient DNA replication?
a. helicase
b. DNA polymerase 1
c. topoisomerase
d. DNA polymerase 3
e. primase
TOPOISOMERASE
A DNA sequence is 3’- GCCACCG-5’
What is the sequence of the primer that begins replication?
5’ - CGGUGGC - 3’
Which of these proteins acts ahead of the replisome to ensure efficient DNA replication?
a. helicase
b. DNA polymerase 1
c. Topoisomerase (DNA gyrase)
d. DNA polymerase 3
e. Primase
TOPOISOMERASE
What is the difference between leading and lagging strands?
a. the leading strand is synthesized 5’ to 3’ while the lagging strand is synthesized 3’ to 5’
b. the leading strand is made of DNA only but the lagging strand is DNA and RNA
c. Initially, the leading strand is continuous while the lagging strand is composed of disconnected fragments
d. the leading strand is synthesized by only DNA polymerase 3 and lagging only by DNA polymerase 1
INITIALLY, THE LEADING STRAND IS CONTINUOUS WHILE THE LAGGING STRAND IS COMPOSED ON DISCONNECTED FRAGMENTS
How does DNA replication in eukaryotes and prokaryotes differ?
a. Eukaryotic DNA replication is not bi-directional
b. Eukaryotic replication occurs only in S phase of the cell cycle while bacteria continuously replicate DNA
c. Replication forks in eukaryotes move more slowly
d. There are fewer DNA polymerases in eukaryotes
e. There are fewer replication origins in eukaryotes
EUKARYOTIC REPLICATION OCCURS ONLY IN THE S PHASE OF THE CELL CYCLE WHILE BACTERIA CONTINUOUSLY REPLICATE DNA
Why would an alkylating agent cause cell death?
a. Uracil is incorporated into the DNA
b. Resulting thymine dimers block replication
c. Causes guanine to pair with adenine
d. Crosslinking between strands blocks replication
CROSSLINKING BETWEEN STRANDS BLOCKS REPLICATION
What is the most common source of mutation in DNA?
a. Chemical mutagens
b. Mismatch
c. Replication Slippage
d. Gamma Irradiation
e. Base Insertion
MISMATCH
The MutS/MutL/MutH mismatch repair system in E. Coli can distinguish daughter strand DNA from parent DNA by:
a. An altered conformation of the daughter DNA due to a recent replication
b. Histones have not yet been added to daughter strand DNA
c. Differential incorporation of heavy and light nitrogen
d. Base methylation present on the parental DNA that is not yet added to the daughter strand
e. That new DNA smell
BASE METHYLATION PRESENT ON THE PARENTAL DNA THAT IS NOT YET ADDED TO THE DAUGHTER STRAND
Which of the following does not play a role in base-excision repair?
a. DNA polymerase
b. DNA ligase
c. Deoxyribose phosphodiesterase
d. Endonuclease
e. All of these play a role
ALL OF THESE PLAY A ROLE
Which of the following is specific to transcription compared to DNA replication?
a. Synthesis proceeds 5’ to 3’ only
b. Requires a primer during initiation
c. 3’ OH of growing chain attacks inner most phosphate of incoming triphosphate
d. Uses ribose triphosphates when growing the chain
e. Synthesis driven by pyrophosphate hydrolysis
USES RIBOSE TRIPHOSPHATES WHEN GROWING THE CHAIN
Which of these is true for both intrinsic and protein-dependent termination?
a. Requires a protein called rho
b. Contains a G-C rich sequence followed by a stretch of U’s
c. The termination signal is coded in the DNA/RNA
d. Forms a hairpin structure
e. ATPase activity allows a protein to pull down on the newly formed RNA
THE TERMINATION SIGNAL IS CODED IN THE DNA/RNA
The lac operon DOES NOT transcribe downstream genes when…
a. Allolactase binds to the repressor
b. B-galactosidase binds to the Lac promoter
c. Glucose levels are high
d. Lactose levels are high
e. CAP with cAMP binds to the operon
GLUCOSE LEVELS ARE HIGH
What TF2 is responsible for recruiting RNA polymerase 2 to the pre-inititation complex?
a. TF2A
b. TF2B
c. TF2E
d. TF2F
e. TF2H
TF2B
How are coactivators recruited to enhance transcription at Estrogen Response Elements?
a. Estradiol binding to the NHR induces a conformational change in the NHR
b. NHR binds to the DNA-binding domain
c. Chromatin becomes tightly coiled by the addition of acetyl groups by HATs
ESTRADIOL BINDING TO THE NHR INDUCES A CONFORMATIONAL CHANGE
Which of the following would you expect for mRNA’s that have a 5’ cap versus those that do not?
a. Decreased rate of degradation and decreased ability to be transcribed
b. Decreased rate of degradation and increased ability to be translated
c. Increased rate of degradation and decreased ability to be translated
d. Increased rate of degradation and increased ability to be transcribed
DECREASED RATE OF DEGRADATION AND INCREASED ABILITY TO BE TRANSCRIBED
What process requires the presence of the sequence 5’ -AAUAAA-3’ in the eukaryotic mRNA transcript?
a. Capping
b. Editing
c. Polyadenylation
d. Splicing
e. tRNA base modification
POLYADENYLATION