🧪 Biotechnology MCQ Quiz Hub

1. The term ‘endonuclease’ refers to cutting the DNA sequence from ______________
only within the polynucleotide chain, not at the ends
the ends of the chain
anywhere in the chain
exactly in the middle of the chain

2. The restriction endonuclease is having a defence mechanism in the bacterial system against foreign DNA such as viruses. But how it is able to protect its own DNA?
By methylation of bacterial DNA by restriction enzyme
By methylation of foreign DNA by restriction enzyme
By phosphorylation of bacterial DNA by restriction enzyme
By phosphorylation of foreign DNA by restriction enzyme

3. Even after replication, how the modified DNA remains protected?
It remains protected because of conservative mode of replication
It remains protected because of semi-conservative mode of replication
The mode of replication has no role to play in the protection
It is again modified after replication

4. How many classes of restriction enzymes are there?
2
1
3
4

5. Type II cuts the sequence in the following way __________
Within the recognition sequence
At 100-1000 nucleotides away from the recognition sequence
At 27-30 nucleotides away from the recognition sequence
It cuts randomly

6. After cleaving the sequence, the nature of the ends created by the type II endonuclease is __________
The ends created are always single stranded
The ends created are always double stranded
Either the ends are single stranded or they are double stranded
One end is single stranded and one end is double stranded

7. A sequence is having two ends, 5’ and 3’. Which of the following statements is correct regarding the nature of the ends?
The 5’ end is having hydroxyl group
The 5’ end is having phosphate group
The 3’ end is having phosphate group
Any group can be present at any end

8. The recognition sequence for BamHI is 5’ G|GATCC 3’. The ‘|’ represents the cutting site. What can be inferred about the ends from it?
The ends created are double stranded
The single stranded end is 5’ in nature
The single stranded end is 3’ in nature
To decide about the nature of the ends more information is needed

9. The recognition sequence of Sau3A is 5’ |GATC 3’ and that for DpnI is 5’ GA|TC 3’. Which of the statements is true?
The ends created by both the enzymes are compatible
The ends created by both the enzymes are not-compatible
The ends created by DpnI are single stranded
The ends created by Sau3A are single stranded

10. The recognition sequence is at times palindromic in nature. Which of the following statements is correct with respect to it?
The molecules which are cut by the same enzyme, anneal only if the sequence is palindromic in nature
When the molecules are cleaved by the same enzyme and the recognition sequence is palindromic in nature, there is no effect on annealing
There are increased chances of annealing if the recognition sequence is palindromic in nature
The term ‘palindromic’ can be used whether the sequence is read from 5’ to 3’ or 3’ to 5’

11. If all the nucleotides are present with equal frequencies and at random, what are the chances of having a particular four nucleotide long motif?
1/256
1/64
1/16
1/8

12. Isoschizomers are defined as ___________
enzymes having same recognition sequence and always cutting at the same site
enzymes having same recognition sequence and always cutting at different site
enzymes having different recognition site and cutting at the same site
enzymes having same recognition site and they may or may not cut at the same site

13. Isocaudomers are defined as the enzymes which recognize different sequence but generate same ends. Which of the following pairs of enzymes can be termed as isocuadomers?
DpnI (GA|TC) and Sau3A (|GATC)
BamHI (G|GATCC) and Sau3A (|GATC)
DpnI (GA|TC) and BglII (A|GATCT)
XbaI (T|CTAGA) and BamHI (G|GATCC)

14. The specificity of an enzyme is affected by the concentration of buffer used. This phenomenon is termed as:
star activity
specificity elevation
concentration gradient effects
diamond activity

15. Which of the following statements is correct with respect to a unit of an enzyme?
One unit of enzyme is defined as the amount of enzyme required to digest 1miligram of standard DNA in a specific time of 1hr and under given temperature conditions
The amount of enzyme required doesn’t vary with the number of sites present in the DNA
If more number of sites is there in the DNA more units of enzyme are required in comparison to same amount of DNA with fewer sites
The amount of enzyme required for digestion of DNA with less number of sites is more than that of more number of sites in the same amount of DNA

16. Which of the following statement is correct regarding partial digestion?
It is defined as the conditions where all the sites in the DNA sequence are not recognized
The number of fragments created by partial digestion are same as that of complete digestion
It is not useful in representation of genomic library
Exactly half of the sites in the DNA are recognized

17. Which of the following is the correct nomenclature of a restriction enzyme obtained from the first activity of strain R of Escherichia coli?
EcoR1
EscRI
EcorI
EcoRI

18. Why is DNase preferred over restriction endonuclease in some cases?
DNase is preferred over restriction endonuclease in some cases because the latter are not able to recognize some of the restriction sites
DNase is more specific as restriction endonuclease, so the required fragment is obtained
DNase is less specific as compared to restriction endonuclease, hence there are more chances of representation of all the possible fragments
DNase is abundant in comparison the restriction endonuclease

19. Besides enzymatic means, physical stress can also be used for cleaving the DNA. Which of the following statements is true?
Sonication, needles, syringes, etc all come under the category of physical stress
In physical stress, there are no chances of contamination
The ends obtained have unique sequences
They are less effective than DNase treatment

20. Phosphatases refer to __________
the enzymes which add phosphate group at the end of the DNA molecule in the place of hydroxyl group
the enzymes which hydrolytically remove phosphate group from the DNA molecules and replace them with hydroxyl group
the enzymes responsible for removal of phosphate group from the DNA molecules and replace them with hydrogen
the enzymes responsible for replacing hydrogen in the DNA molecules with the phosphate group

21. How is phosphatase related to the ligation reactions?
Phosphate group is not required for the ligation reaction to take place, thus phosphatase is helpful
It is helpful in ceasing the unwanted ligation
Phosphatases are not at all related to ligation reactions
They act as a catalyst in case of the ligation reaction

22. How can phosphatase activity terminated prior to a ligation reaction?
By heating
By cooling
By creating vibrations
By alternatively cooling and heating

23. Basic classification of polymerases includes how many types?
2
3
4
5

24. Polymerase can be defined as ______________
an enzyme used to synthesize a new DNA or RNA strand on the basis of pre-existing strand or at times without a pre-existing strand
an enzyme used for removal of nucleotides from the DNA or RNA strand
an enzyme which can synthesize only a new DNA strand, not an RNA strand
an enzyme which can synthesize either a new DNA or an RNA strand but only when a strand is there

25. Which of the following activity is not possible in the case of DNA polymerase I?
3’-5’ exonuclease
5’-3’ exonuclease
5’-3’ DNA synthesis
3’-5’ DNA synthesis

26. The E. coli DNA polymerase enzyme gives different domains with different activities on cleaving with protease subtilisin. Which of the following statements is correct with respect to the fragments generated?
The smaller fragment is having C terminal and the larger fragment is having N terminal
The smaller fragment is named as Klenow fragment and the intact molecule is called as Kornberg fragment
The smaller fragment is having 5’-3’ exonuclease activity whereas the larger fragment is having 5’-3’ polymerase and 3’-5’ exonuclease activity
Both the fragments are having 5’-3’ polymerase and 3’-5’ exonuclease activity

27. Removal of single stranded portions produced due to exonucleolytic activity and due to polymerase activity are termed as _____________
polishing and end filling respectively
end filling and polishing respectively
polishing in both the cases
end filling in both the cases

28. Thermostable DNA polymerases are very important in PCR. How are they obtained?
They are obtained by heating the bacteria manually over high tempere isolated from extremely stable thermophilic bacteria which are often founratures
They ad growing in oceanic vents
They are found everywhere in nature
They are obtained by genetically modifying the E. coli bacteria with thermal stability property

29. Which of the following enzyme is said as reverse transcriptase?
DNA dependent DNA polymerase
RNA dependent RNA polymerase
RNA dependent DNA polymerase
DNA dependent RNA polymerase

30. Why reverse transcriptase enzymes are having comparatively high error rates than other polymerases?
Because they are not having 3’-5’ proofreading exonucleolytic activity
Because they are not having 5’-3’ proofreading exonucleolytic activity
Because they are having slow rates of exonucleolytic activity
It is difficult to synthesize DNA from RNA

31. Which polymerase can be used in conjunction with appropriate phage promoters in order to have high levels of specific transcription?
RNA dependent DNA polymerase
DNA dependent RNA polymerase
RNA dependent RNA polymerase
DNA dependent DNA polymerase

32. Template independent polymerases are the enzymes which add nucleotide bases without a template. Which of the following statements is correct with respect to these?
They only add a single nucleotide
They only add a string of nucleotides and not a single nucleotide
Terminal transferase adds a series of nucleotides at the 3’ end
Taq polymerase adds a single nucleotide at the 5’ end of the PCR product

33. Which of the following statements is correct with respect to exonuclease?
They only act on single stranded DNA molecules
They only act on double stranded DNA molecules
They remove a single nucleotide base at a time
They remove nucleotide bases from the middle of a polynucleotide chain

34. How many approaches are there which can be used for exonucleolytic activity in double stranded DNA molecules?
1
2
3
4

35. What is the mode of action of exonuclease III?
Exonuclease III acts on single stranded DNA in 3’-5’ direction
Exonuclease III acts on double stranded DNA in 5’-3’ direction
Exonuclease III acts on single stranded DNA in 5’-3’ direction
Exonuclease III acts on double stranded DNA in 3’-5’ direction

36. Which of the following statements is correct regarding S1 nuclease?
It acts on double stranded DNA
It acts on single stranded DNA
It acts on both types of strands
It is obtained from E. coli

37. What happens if a DNA molecule is treated by first Exonuclease III and then followed by treatment with S1 nuclease?
The molecule is shortened only from 3’ end
The molecule is shortened only from 5’ end
The molecule is shortened from both the ends
Only Exonuclease acts and S1 doesn’t acts

38. How can one end be protected from the action of Exonuclease III, so that the molecule is not shortened from both the ends?
By using Phosphorothioate nucleotide analogue
By making both the ends double stranded in nature
By labelling one end with a radioactive compound
By increasing the time of exposure of the DNA molecule to the enzyme

39. Bal31 is also an enzyme which is used. Which of the following statements hold true in its context?
It is having only 3’-5’ exonuclease activity and no endonuclease activity
It is having only an endonuclease activity
It is having 5’-3’ exonuclease activity
It leads to shortening from both the ends

40. The extent of deletions can be manipulated by controlling which of them?
Time of incubation only
Amount of nuclease added
They both have a role to play in the extent of the deletion
The amount of deletion which can be carried out for a particular amount of DNA is fixed regardless of the amount of nuclease and incubation time

41. What is the function of methylase?
Addition of methyl groups to DNA
Removal of methyl groups from DNA
Both in removal and addition of methyl groups from DNA
It is used in production of methane gas

42. Ligation is defined as ______________
Alignment of only double stranded DNA molecules at the ends and the formation of phosphodiester bonds between both the strands
Alignment of either of the double or single stranded DNA molecules and formation of glycosidic bonds between both the strands
Alignment of either of the double or single stranded DNA molecules and the formation of phosphodiester bonds. The bond can be between either one or both the strands
Alignment of single stranded DNA molecules and formation of glycosidic bonds between these strands

43. If only one bond is broken in the sugar-phosphate backbone, it is called as ___________
gap
nick
break
leakage

44. How many categories of ligation reaction are there on the basis of ends created?
1
2
3
4

45. In the case of blunt-end ligation, blunt ends can be generated by ___________
simply the action of restriction endonuclease which gives straight ends
the polishing of staggered ends
both the action of restriction endonuclease which gives straight ends and polishing of staggered ends
by the action of restriction endonuclease which gives staggered ends

46. The ligation reaction is more efficient in which case?
Blunt end ligation
Sticky end ligation
Both have the same efficiency
Depends on the reaction conditions

47. The sticky ends are held together by which type of bonds?
Hydrogen bond
Covalent bond
Ionic bond
Van-der-waal forces

48. Why sticky ended ligations are carried out at temperatures lower than room temperature?
It is so because the vibrational and kinetic energy of the molecules at room temperature is lower than that of the energy required to break the bonds holding the ends
The energy required to break the bonds holding the ends is very less than that of the kinetic and vibrational energy at room temperature
The enzyme carrying out ligation is unstable at low temperature
The sticky ends created, don’t just relegate at low temperature

49. If a ligation reaction is being carried out and recircularization is observed, which type of reaction is being carried out?
Intramolecular
Intermolecular
Both observe recircularization equally
Recirculation is not possible in any of the cases

50. What is the kinetics of the intramolecular and intermolecular ligation reactions?
Second order kinetics for intramolecular and first order for intermolecular
First order kinetics for intramolecular and second order for intermolecular
Both are first order
Both are second order