2017 biochem midterm

Question 1

Which polymerase possesses 5’ —— 3’ exonuclease activity in prokaryotes?

a. DNA polymerase 3
b. DNA polymerase 2
c. DNA polymerase 4
d. DNA polymerase 1

Answer 1

d. DNA polymerase 1

Question 2

If you choose annealing temperature higher than the melting temperature of your primer. What will happen to the PCR reaction?

a. Taq polymerase denaturation
b. Failure of DNA separation
c. Failure of primer binding
d. Formation of primer dimer

Answer 2

c. Failure of primer binding

Question 3

What serves as an allosteric inhibitor of pyruvatic dehydrogenase-kinase?

a. Acetyle coA
b. Mg+2
c. NAD+
d. NADH

Answer 3

c. NAD+

Question 4

During which PCR step does DNA synthesis occur?

a. Annealing
b. Denaturation
c. Extension
d. Storage

Answer 4

c. Extension

Question 5

What is the primary function of NADPH / NADP?

a. Anabolic
b. Catabolic
c. Oxidation
d. Phosphorylation

Answer 5

a. Anabolic

Question 6

What is the most common deleted amino acid in cystic fibrosis?

a. GLY 509
b. ISO 506
c. ISO 507
d. PHE 508

Answer 6

d. PHE 508

Question 7

Which translation step will be inhibited if an antibiotic binds to the A site of the ribosome?

a. Initiation
b. Elongation
c. Termination
d. Charging of tRNA

Answer 7

b. Elongation

Question 8

Which force stabilizes a secondary structure of a protein?

a. H bonds
b. Hydrophobic interactions
c. Peptide bonds
d. S-S bonds

Answer 8

a. H bonds

Question 9

Which epigenetic change is likely to inhibit gene expression?

a. Cytosine
b. Guanosine
c. Adenine

Answer 9

a. Cytosine

Question 10

Restriction endonucleases work on what?

a. Single stranded RNA
b. Single stranded DNA
c. Double stranded RNA
d. Double stranded DNA

Answer 10

d. Double stranded DNA

Question 11

Which test is used to diagnose patients with cystic fibrosis?

a. Free ion test
b. Pulmonary function test
c. Blood lipase test
d. Sweat test

Answer 11

d. Sweat test

Question 12

Which percentage of the genome do repetitive elements contribute to?

a. 60%
b. 47%
c. 23%
d. 10%

Answer 12

b. 47%

Question 13

Which of the following allows reaction catalyzed by glyceraldehyde -3- phosphate dehydrogenase when glucose is metabolized anaerobicly?

a. NADH oxidation by lactate dehydrogenase
b. Reduction of NAD+ to NADH in mitochondria

Answer 13

a. NADH oxidation by lactate dehydrogenase

Question 14

What is the function of tge Srn protein?

a. Cytosol phosphorylation
b. Nucleus transcription actor
c. Membranous receptor

Answer 14

a. Cytosol phosphorylation

Question 15

Which type of point mutation is involved in converting purine to pyrimidine?

a. Transposition
b. Transition
c. Deletion
d. Transversion

Answer 15

d. Transversion

Question 16

What are transcription factors?

a. Catalytic molecules
b. Cis acting proteins
c. DNA segments
d. Regulating proteins

Answer 16

d. Regulating proteins

Question 17

On which site does aa- tRNA binds in elongation?

a. A site
b. P site
c. E site

Answer 17

a. A site

Question 18

What is the natural function of restricting enzymes?

a. Protecting bacteria by cleaving the DNA of infecting viruses
b. Protecting bacteria by degrading the RNA of infecting viruses
c. Protecting bacteria by methylating their RNA
d. Protecting bacteria by methylating the DNA of infecting viruses

Answer 18

a. Protecting bacteria by cleaving the DNA of infecting viruses

Question 19

At which level is apo B regulated?

a. MRNA editing
b. MRNA splicing
c. Formation of poly A tail

Answer 19

a. MRNA editing

Question 20

Which of the following use glucagon stores to increase blood glucose?

a. Skeletal muscles
b. Liver
c. Kidney
d. Adipose

Answer 20

b. Liver

Question 21

Which of the following is the main product of non-oxidized pentose phosphate pathway?

a. Ribose -5- phosphate
b. Glucose -6- phosphate
c. Conversion of AMP and ADP to ATP
d. Reducing NAD+ to NADH

Answer 21

a. Ribose -5- phosphate

Question 22

Which of the following causes the base selective termination?

a. DDNTP
b. DNTP

Answer 22

a. DDNTP

Question 23

Which pairs are products of catabolic pathway?

a. ATP , NADH
b. ATP , NAD+
c. ADP , NADH
d. ADP , NAD+

Answer 23

a. ATP , NADH

Question 24

What is the main step that regulates a metabolic pathway?

a. First reaction that leads only to the product
b. Last reaction in the pathway
c. Fastest reaction in the pathway
d. If delta G = 0

Answer 24

a. First reaction that leads only to the product

Question 25

To which human genome do Alu elements belong? a. Long terminate repeat sequence b. Long interspersed sequence c. Short interspersed sequence d. Tandem repeat sequence

Answer 25

c. Short interspersed sequence

Question 26

In PCR experiment we use only single strand DNA, what would be the product number If we do 20 cycles? a. 20 b. 40 c. 60

Answer 26

a. 20

Question 27

What characterizes a prion? a. Change in alpha helices b. Change in beta sheets c. Change in primary protein structure

Answer 27

b. Change in beta sheets

Question 28

What is the theory behind Alzheimer’s disease? a. Protein synthesis b. Protein processing c. Protein infolding d. Protein secretion

Answer 28

b. Protein processing

Question 29

What is the characteristic of isozymes? a. Same product and substrate b. Same sub-cellular locations c. Same coenzyme

Answer 29

a. Same product and substrate

Question 30

What activates zymogen into an active enzyme? a. Proteolysis b. Oxidation c. Phosphorylation

Answer 30

a. Proteolysis

Question 31

Why is the template DNA invisible in agarose gel? a. DNA template resolves into the gel b. DNA template hydrolyzed c. Amount of template isn’t enough

Answer 31

c. Amount of template isn’t enough

Question 32

What does camptothecin inhibit? a. DNAa b. Topoisomerase 1 c. Topoisomerase 2

Answer 32

b. Topoisomerase 1

Question 33

What is the most abundant in RNA? a. rRNA b. tRNA c. mRNA

Answer 33

a. rRNA

Question 34

Which of the following is involved in rRNA processing? a. SnRNA b. SnoRNA c. TRNA

Answer 34

b. SnoRNA

Question 35

Energy released from reduction of O2 to water is used in? a. Pumping H+ b. Substrate – level phosphorylation

Answer 35

a. Pumping H+

Question 36

What stimulates gluconeogenesis? a. high activity of fructose 2,6 bisphosphate b. low activity of fructose 2,6 bisphosphate c. epinephrine

Answer 36

low activity of fructose 2,6 bisphosphate

Question 37

What does the acetylation of Arg in histone do? a. surpasses negative charge of histone tail b. surpasses positive charge of histone tail c. strengthen histone to DNA binding

Answer 37

b. surpasses positive charge of histone tail

Question 38

What causes the activation of RAS proto-oncogene? a. Translocation b. Point mutation c. Gene deletion

Answer 38

b. Point mutation

Question 39

How does glycosyl transferase sense that a protein is unfolded? a. Presence of alpha-helical structure b. Presence of beta structure c. Presence of exposed hydrophobic aa d. Presence of peptide bond

Answer 39

c. Presence of exposed hydrophobic aa

Question 40

What is a general property of an allosteric site? a. High affinity for substrate and product b. Ligand binding influences protein conformation c. High affinity for coenzyme d. Formed by covalently attached prosthetic groups

Answer 40

b. Ligand binding influences protein conformation