Biochemistry MCQ Quiz Hub

1. The chromosomal DNA complexes with
three types of histone as H1, H2A and H4
five types of histone as H1, H2A, H2B, H3 and H4
four types of histone as H1, H2A, H3 and H4
two types of histone as H1 and H4

2. Taylor, Woods and Hughes labeled Vicia DNA by allowing new DNA synthesis in the presence of radioactive thymine. After DNA replication (S phase of the cell cycle), it was observed that
only one chromatid of a chromosome was labeled
both chromatids of a chromosome were labeled
both (a) and (b)
neither chromatid was labeled

3. In DNA double helix, the two DNA chains are held together by
covalent bonds between the pair of bases
hydrogen bonds between the pair of bases
ionic bonds between the pair of bases
none of the above

4. The 5' and 3' numbers are related to the
length of the DNA strand
carbon number in sugar
the number of phosphates
the base pair rule

5. Messelsen and Stahl model of replication was called
conservative replication
semi-conservative replication
dispersive replication
Cri du Chat

6. he most common liquid volumes in molecular biology are measured in
ml
μl
nl
1

7. DNA replication takes place in which direction?
3' to 5'
5 'to 3'
Randomly
Vary from organism to organism

8. DNA gyrase in E. coli
adds positive supercoils to chromosomal DNA
can be inhibited with antibiotics
is required only at the oriC site
performs the same function as helicase in eukaryotes

9. In DNA, there are
five bases known as adenine, guanine, thymine, tryptophan and cytosine
four bases known as adenine, guanine, thymine and cytosine
three bases known as adenine, guanine and cytosine
only two bases known as adenine and cytosine

10. In DNA, guanine pairs with
Adenine
Cytosine
Thymine
Uracil

11. Which of the following is incorrect?
In DNA double helix, two strands of the DNA are bound with each other with the bases
Adenine always pairs with thymine
Guanine always pairs with the cytosine
None of the above

12. What is the only common methylation in the DNA of eukaryotes?
Adenosine in GpA dinucleotides
Guanosine in ApGpA trinucleotides
Cytosine in CpG dinucleotides
None of the above

13. DNAs when charged, migrate in a gel towards the
positive pole
negative pole
will not migrate
none of these

14. What is the approximate size (in kb) of the E. coli genome?
3000 kilobase
45000 kilobase
55000 kilobase
65000 kilobase

15. In the study of one experiment it was found that the value of Tm for DNA is = 40° C. If the cell has 20% GC at the above Tm, then what will be value of 'Tm' if the GC% increases to 60%?
Remains same
Increases
Decreases
Can not be compared

16. What is the range of melting point temperatures (Tm) for most DNA molecules?
50 to 60°C
60 to 80°C
70 to 90°C
80 to 100°C

17. The overall conclusion of the Hershey-Chase experiment was that
DNA was responsible for heredity
proteins and DNA were responsible for heredity
the ratio of Adenine to thymine was always the same
phage DNA was similar to bacterial DNA

18. A cesium chloride will separate DNA molecules by
absorption
resorption
density
adhesion

19. If one cell has AT contents 40%, what will be the percentage of Guanine residue?
60%
15%
30%
Guanine residue can not be calculated

20. Which of the following enzyme adds complementary bases during replication?
Helicase
Synthesase
Replicase
Polymerase

21. Which DNA polymerase removes RNA primers in DNA synthesis?
Polymerase I
Polymerase II
Polymerase III
none of these

22. Enzymes, responsible for unraveling short segments of DNA is
DNA polymerase
helicase
DNA ligase
Primase

23. Enzyme, responsible for proofreading base pairing is
DNA polymerase
Telomerase
Primase
DNA ligase

24. Which of the following would not contain DNA?
Yeast
Bacteria
Glass crystals
Mold

25. The nucleosome consists of histone
octamer and 146 bp of DNA
tetramer and 146 bp of DNA
hexamer and 146 bp of DNA
none of the above

26. What bands will be observed in a cesium chloride gradient after two rounds of replication?
One light, one medium and one heavy band
One light and one medium band
One medium band
One medium and one heavy band

27. Proteins involved in opening a replication bubble are
DNA helicases
single stranded binding proteins
ligase
DNA topoisomerase

28. What is the main damaging effect of UV radiation on DNA?
Depurination
Formation of thymine dimers
Single strand break
Dehydration

29. The higher order structure of DNA shows symmetry, whereas the higher order structures of most proteins do not. Why isn't protein shape more regular like DNA?
DNA has one main function in cells whereas proteins have many.
The many different amino acid R groups on proteins confer many different shapes.
Some S amino acids cause proteins to bend; others cause protein to flatten.
All of the above

30. DNA helicase is used to
unwind the double helix
interact the double helix closely
break a phosphodiester bond in DNA strand
none of the above

31. Klenow fragment without free nucleotides exhibits
exonuclease activity
endonuclease activity
nickase activity
no activity

32. E.coli DNA polymerases II and III lack
5' → 3' exonuclease activity
5' → 3' endonuclease activity
partially 5' → 3' exonuclease activity
partially 5' → 3' endonuclease activity

33. In sperm heads, DNA is particularly highly condensed and the histones are replaced with small basic protein called
protamines
purines
pyrimidines
all of the above

34. Okazaki fragments occur during
transformation
replication
polymerase reaction
synthesis

35. DNA can be sequenced by the
chemical method
chain termination procedure
both (a) and (b)
physical method

36. Each replication bubbles consists of
3 replication forks
2 replication forks
4 replication forks
1 replication forks

37. n DNA replication, one new strand is synthesized complementary to an old (parent) strand and is referred as
mutational
semiconservative
discontinuous
antiparallel

38. In a cesium chloride gradient, DNA labeled with 15N and centrifuged will form a band
above DNA containing 14N
below DNA containing 14N
with 14N-containing DNA
all of these

39. The role of primase is to
dismantle RNA primer
cleave and unwinds short sections of DNA ahead of the replication fork
proofread base pairing
synthesize an RNA primer to begin the elongation process

40. Deoxyribonucleoside triphosphates, being need in the chain termination methods are
dATP
dGTP and dCTP
dTTP
all of these

41. What is the approximate percentage of repetitive DNA sequences in human DNA?
10 to 20%
20 to 30%
30 to 40%
40 to 50%

42. The replication of a linear DNA molecule in a eukaryotic chromosome creates a problem which is reported to be sorted out by
using enzyme called telomerase
shortening of the double stranded replicated portion
using RNA as a template
none of the above

43. The rapid appearance of HIV-1 strains that are resistant to AIDS drugs is due in part to which of the following property of its reverse transcriptase?
AZT (zidovudine) is too expensive to be taken in effective doses
The RNase H domain of p66 causes error prone synthesis
It lacks a proofreading exonuclease
It has low affinity for the correct dNTP's

44. The packing ratio of nucleosomes is about
6
8
7
9

45. After one replication in 15N, how many bands should be observed in a cesium chloride gradient?
One
Two
Three
A smear

46. Reverse transcriptase produces
DNA from peptides
RNA from DNA
RNA from RNA
DNA from RNA

47. The nicks or gaps between Okazaki fragments are eventually sealed by
gyrase
DNA ligase
RNA ligase
polymerase

48. Nucleosome is
an octamer of four histones with H1 protein
an hexamer of three histones with H1 protein
an hexamer of three histones without H1 protein
an octamer of four histones without H1 protein

49. The DNA polymerase in bacteria, responsible for DNA synthesis is
Polymerase I
Polymerase II
Polymerase III
all of these

50. In a typical electrophoresis experiment, larger fragments of DNA move more
slowly, so they appear nearer the top of a gel photograph
quickly, so they appear nearer the top of a gel photograph
slowly, so they appear nearer the bottom of a gel photograph
quickly, so they appear nearer the bottom of a gel photograph

51. 30 nm wide helix with five or six nucleosomes per helix is known as
solenoid
halonoid
kinoplast
none of these

52. Which of the following is used to determine the appropriate stringency (Wallace rule)?
Tm = 2 x (No.of G:C base pair) + 4 x (No.of A:T base pair)
Tm = 4 x (No.of A:T base pair) + 2 x (No.of G:C base pair)
Tm = 4 x (No.of G:C base pair) + 2 x (No.of A:T base pair)
Tm = 69.3° + 0.41 (%)G+C -650/1

53. One hypothesis of DNA replication suggested that the parental DNA molecules are broken into fragments. Both strands of DNA in each of the daughter molecules are made up of an assortment of parental and new DNA. This statement refers to which hypothesis?
Conservative theory
Dispersive theory
Semi-conservative theory
Evolutionary theory

54. DNA polymerases I also has
5'-3' exonuclease activity
3'-5'exonuclease activity
both (a) and (b)
5'-3' endonuclease activity

55. Without telomerase, what would happen to the ends of chromosomes after each round of replication?
Chromosomes would become progressively shorter
Nothing would happen
Chromosomes would get longer
none of the above

56. The melting of 40-45 bp at the oriC site of E. coli requires
DNA + ATP + HU
DNA + ATP + HU + DNAb
DNA+ ATP + HU + DNAb + DNAa
DNA + ATP + HU + DNAb + DNAa + Pol III holoenzyme