2010 biochem midterm

Question 1

What is the last step of DNA replication?

a. filling in RNA primase gaps with DNA
b. ligation of Okazaki fragments
c. relaxing the supercoiled DNA

Answer 1

b. ligation of Okazaki fragments

Question 2

How can you indicate intron?

a. 5’ CA - AT 3’
b. 5 CA - AT 3
c. 5 GU - AG 3
d. 5’ GU - AG 3’

Answer 2

d. 5’ GU - AG 3’

Question 3

Which RNA is synthesized by RNA polymerase III?

a. mRNA
b. tRNA
c. rRNA

Answer 3

b. tRNA

Question 4

What best characterizes euchromatin?

a. actively transcripted
b. most inactive DNA segment
c. condensed chromatin

Answer 4

a. actively transcripted

Question 5

Which system is the most affected by cystic fibrosis? 
A. Respiratory system
B. Nervous system
C. Musculoskeletal system 
D. Circulatory system

Answer 5

A. Respiratory system

Question 6

Why does ddNTP stop DNA synthesis?

a. it’s tagged
b. it doesn’t provide 3OH
c. it blocks mRNA
d. it blocks tRNA

Answer 6

b. it doesn’t provide 3OH

Question 7

What causes mad cow disease (prion disease)?

a. Incorrect protein folding
b. point mutation
c. protein degradation error

Answer 7

a. Incorrect protein folding

Question 8

Which mechanism is used to repair xeroderma pigmentosum?

a. Base excision repair
b. Mismatch repair system
c. Nucleotide excision repair

Answer 8

c. Nucleotide excision repair

Question 9

What is the activated form of glucose that synthesizes glycogen? 
A. UDP-glucose
B. G-6-P 
C. G-1-P
D. UTD-glucose

Answer 9

A. UDP-glucose

Question 10

What type of mutation occurs in phenylketonuria?

a. frameshift
b. silent
c. nonsense
d. missense

Answer 10

d. missense

Question 11

What is the most common type of mutation affecting the fibrillin-1 gene?

a. nonsense
b. missense
c. frameshift
d. silent

Answer 11

b. missense

Question 12

Which domain is affected by CFTR?

a. ATP domain
b. Ig-type domain
c. gene duplication domain

Answer 12

a. ATP domain

Question 13

Laboratory assay had a sample with IU=2 and a protein of 10 mg, what is the specified activity?

a. 0.1
b. 0.2
c. 0.5

Answer 13

b. 0.2

IU/MASS = 2/10

Question 14

In somatic cells of eukaryotes, what leads to shortening of the chromosome?

a. Low telomerase activity
b. High telomerase activity
c. Low RNase activity
d. High RNase activity

Answer 14

a. Low telomerase activity

Question 15

What snrnp bind to 5’ end of intron?

a. U1
b. U2
c. U3
d. U4

Answer 15

a. U1

Question 16

What is the function of restriction enzyme?

a. Cleavage of RNA at specific sites
b. Cleavage of DNA at specific sites
c. Reduce the bacterial grown to enhance the viral control
d. Protein degradation

Answer 16

b. Cleavage of DNA at specific sites

Question 17

What groups of amino acids form peptide bonds in a protein?

a. side chain
b. α NH2 and α COO
c. hydrogen

Answer 17

b. α NH2 and α COO

Question 18

What is proto-oncogenes?

a. genes that may be converted to oncogenes
b. cancerous genes
c. genes filled with mutations

Answer 18

a. genes that may be converted to oncogenes

normal genes which, when altered by mutation, become oncogenes that can contribute to cancer

Question 19

Penicillin is a suicide inhibitor, why?

a. It inhibits cell suicide (apoptosis)
b. It interacts covalently with the enzyme
c. It phosphorylates the cell surface

Answer 19

b. It interacts covalently with the enzyme

Question 20

Which of the following undergoes hydrolyxation?

a. Proteins
b. RNA
c. DNA
d. Collagen

Answer 20

d. Collagen

Question 21

If we have 20 PCR cycle, how many initial folds would we have in DNA sequencing?

a. 4 folds
b. 10 folds
c. 20 folds
d. 35 folds

Answer 21

c. 20 folds

Question 22

Which of the following is used in DNA fingerprinting?

a. Minisatellite
b. PCR

Answer 22

a. Minisatellite

Question 23

What is the effect of vitamin C in synthesizing collagen?

Answer 23

Hydroxylation of proline

Question 24

Which of the following will be inhibited if antibiotics stopped the formation of 30s complex?

a. elongation
b. initiation
c. folding

Answer 24

b. initiation

Question 25

Which of the following binds to lysosomal protein?

a. G-1-P
b. M-3-P
c. M-6-P
d. G-6-P

Answer 25

c. M-6-P

Question 26

Calcitonin expression is changed at which stage?

Answer 26

Polyadenylation and splicing

Question 27

Which of the following is true concerning allosteric enzymes?

a. always increase enzymatic activity
b. always decrease enzymatic activity
c. bind outside the active site

Answer 27

c. bind outside the active site

Question 28

What is the function of glycogenin in glycogen?

a. Act as a primer in glycogen formation
b. Secures the edges of glycogen are closed

Answer 28

a. Act as a primer in glycogen formation

Question 29

Where unfolded proteins are degraded?

a. Cytosol
b. Golgi
c. ER
d. Lysosomes

Answer 29

c. ER

Question 30

What is the difference in the initiation stage between eukaryotic & prokaryotic translation?

Answer 30

Searching for the start codon in the sequence

Question 31

What is the mutation of collagen structure in osteogenesis that’s imperfect?

Answer 31

Covalent bond OR (disulfide bond)

Question 32

What leads to the accumulation of hemoglobin in sickle cell disease?

Answer 32

Deoxygenation

Question 33

What is a metaphasic chromosome?
A. uncompacted DNA
B. naked DNA molecule without histones 
C. single-stranded DNA 
D. double-stranded DNA molecule with histones
E. 4 DNA stands with histones

Answer 33

E. 4 DNA stands with histones

Question 34

As temperature increases, it has a negative effect on the activity of the enzyme, what is the best epanation for the decline?
A. Enzyme denaturation
B. ∆G ↓
C. Activation E ↓

Answer 34

A. Enzyme denaturation

Question 35

What is the structure of metaphasic chromosome?
A. Naked DNA protein without histones
B. Double strand DNA molecule with histones
C. Four strands of DNA with histones

Answer 35

C. Four strands of DNA with histones