Olete.in – MCQs, Mock Tests & Government Job Prep | Biotechnology Biotechnology MCQ set-1

The term ‘endonuclease’ refers to cutting the DNA sequence from ______________

1. only within the polynucleotide chain, not at the ends
2. the ends of the chain
3. anywhere in the chain
4. exactly in the middle of the chain

✅ Correct Answer: 1

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?

1. By methylation of bacterial DNA by restriction enzyme
2. By methylation of foreign DNA by restriction enzyme
3. By phosphorylation of bacterial DNA by restriction enzyme
4. By phosphorylation of foreign DNA by restriction enzyme

✅ Correct Answer: 1

Even after replication, how the modified DNA remains protected?

1. It remains protected because of conservative mode of replication
2. It remains protected because of semi-conservative mode of replication
3. The mode of replication has no role to play in the protection
4. It is again modified after replication

✅ Correct Answer: 2

How many classes of restriction enzymes are there?

1. 2
2. 1
3. 3
4. 4

✅ Correct Answer: 3

Type II cuts the sequence in the following way __________

1. Within the recognition sequence
2. At 100-1000 nucleotides away from the recognition sequence
3. At 27-30 nucleotides away from the recognition sequence
4. It cuts randomly

✅ Correct Answer: 1

After cleaving the sequence, the nature of the ends created by the type II endonuclease is __________

1. The ends created are always single stranded
2. The ends created are always double stranded
3. Either the ends are single stranded or they are double stranded
4. One end is single stranded and one end is double stranded

✅ Correct Answer: 3

A sequence is having two ends, 5’ and 3’. Which of the following statements is correct regarding the nature of the ends?

1. The 5’ end is having hydroxyl group
2. The 5’ end is having phosphate group
3. The 3’ end is having phosphate group
4. Any group can be present at any end

✅ Correct Answer: 2

The recognition sequence for BamHI is 5’ G|GATCC 3’. The ‘|’ represents the cutting site. What can be inferred about the ends from it?

1. The ends created are double stranded
2. The single stranded end is 5’ in nature
3. The single stranded end is 3’ in nature
4. To decide about the nature of the ends more information is needed

✅ Correct Answer: 2

The recognition sequence of Sau3A is 5’ |GATC 3’ and that for DpnI is 5’ GA|TC 3’. Which of the statements is true?

1. The ends created by both the enzymes are compatible
2. The ends created by both the enzymes are not-compatible
3. The ends created by DpnI are single stranded
4. The ends created by Sau3A are single stranded

✅ Correct Answer: 2

The recognition sequence is at times palindromic in nature. Which of the following statements is correct with respect to it?

1. The molecules which are cut by the same enzyme, anneal only if the sequence is palindromic in nature
2. When the molecules are cleaved by the same enzyme and the recognition sequence is palindromic in nature, there is no effect on annealing
3. There are increased chances of annealing if the recognition sequence is palindromic in nature
4. The term ‘palindromic’ can be used whether the sequence is read from 5’ to 3’ or 3’ to 5’

✅ Correct Answer: 3

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. 1/256
2. 1/64
3. 1/16
4. 1/8

✅ Correct Answer: 1

Isoschizomers are defined as ___________

1. enzymes having same recognition sequence and always cutting at the same site
2. enzymes having same recognition sequence and always cutting at different site
3. enzymes having different recognition site and cutting at the same site
4. enzymes having same recognition site and they may or may not cut at the same site

✅ Correct Answer: 4

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?

✅ Correct Answer: 2

The specificity of an enzyme is affected by the concentration of buffer used. This phenomenon is termed as:

1. star activity
2. specificity elevation
3. concentration gradient effects
4. diamond activity

✅ Correct Answer: 1

Which of the following statements is correct with respect to a unit of an enzyme?

1. 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
2. The amount of enzyme required doesn’t vary with the number of sites present in the DNA
3. 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
4. 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

✅ Correct Answer: 3

Which of the following statement is correct regarding partial digestion?

1. It is defined as the conditions where all the sites in the DNA sequence are not recognized
2. The number of fragments created by partial digestion are same as that of complete digestion
3. It is not useful in representation of genomic library
4. Exactly half of the sites in the DNA are recognized

✅ Correct Answer: 1

Which of the following is the correct nomenclature of a restriction enzyme obtained from the first activity of strain R of Escherichia coli?

1. EcoR1
2. EscRI
3. EcorI
4. EcoRI

✅ Correct Answer: 4

Why is DNase preferred over restriction endonuclease in some cases?

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

✅ Correct Answer: 3

Besides enzymatic means, physical stress can also be used for cleaving the DNA. Which of the following statements is true?

1. Sonication, needles, syringes, etc all come under the category of physical stress
2. In physical stress, there are no chances of contamination
3. The ends obtained have unique sequences
4. They are less effective than DNase treatment

✅ Correct Answer: 1

Phosphatases refer to __________

1. the enzymes which add phosphate group at the end of the DNA molecule in the place of hydroxyl group
2. the enzymes which hydrolytically remove phosphate group from the DNA molecules and replace them with hydroxyl group
3. the enzymes responsible for removal of phosphate group from the DNA molecules and replace them with hydrogen
4. the enzymes responsible for replacing hydrogen in the DNA molecules with the phosphate group

✅ Correct Answer: 2

How is phosphatase related to the ligation reactions?

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

✅ Correct Answer: 2

How can phosphatase activity terminated prior to a ligation reaction?

1. By heating
2. By cooling
3. By creating vibrations
4. By alternatively cooling and heating

✅ Correct Answer: 1

Basic classification of polymerases includes how many types?

1. 2
2. 3
3. 4
4. 5

✅ Correct Answer: 4

Polymerase can be defined as ______________

1. 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
2. an enzyme used for removal of nucleotides from the DNA or RNA strand
3. an enzyme which can synthesize only a new DNA strand, not an RNA strand
4. an enzyme which can synthesize either a new DNA or an RNA strand but only when a strand is there

✅ Correct Answer: 1

Which of the following activity is not possible in the case of DNA polymerase I?

1. 3’-5’ exonuclease
2. 5’-3’ exonuclease
3. 5’-3’ DNA synthesis
4. 3’-5’ DNA synthesis

✅ Correct Answer: 4

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?

1. The smaller fragment is having C terminal and the larger fragment is having N terminal
2. The smaller fragment is named as Klenow fragment and the intact molecule is called as Kornberg fragment
3. The smaller fragment is having 5’-3’ exonuclease activity whereas the larger fragment is having 5’-3’ polymerase and 3’-5’ exonuclease activity
4. Both the fragments are having 5’-3’ polymerase and 3’-5’ exonuclease activity

✅ Correct Answer: 3

Removal of single stranded portions produced due to exonucleolytic activity and due to polymerase activity are termed as _____________

1. polishing and end filling respectively
2. end filling and polishing respectively
3. polishing in both the cases
4. end filling in both the cases

✅ Correct Answer: 1

Thermostable DNA polymerases are very important in PCR. How are they obtained?

1. They are obtained by heating the bacteria manually over high tempere isolated from extremely stable thermophilic bacteria which are often founratures
2. They ad growing in oceanic vents
3. They are found everywhere in nature
4. They are obtained by genetically modifying the E. coli bacteria with thermal stability property

✅ Correct Answer: 2

Which of the following enzyme is said as reverse transcriptase?

1. DNA dependent DNA polymerase
2. RNA dependent RNA polymerase
3. RNA dependent DNA polymerase
4. DNA dependent RNA polymerase

✅ Correct Answer: 3

Why reverse transcriptase enzymes are having comparatively high error rates than other polymerases?

1. Because they are not having 3’-5’ proofreading exonucleolytic activity
2. Because they are not having 5’-3’ proofreading exonucleolytic activity
3. Because they are having slow rates of exonucleolytic activity
4. It is difficult to synthesize DNA from RNA

✅ Correct Answer: 1

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

1. RNA dependent DNA polymerase
2. DNA dependent RNA polymerase
3. RNA dependent RNA polymerase
4. DNA dependent DNA polymerase

✅ Correct Answer: 2

Template independent polymerases are the enzymes which add nucleotide bases without a template. Which of the following statements is correct with respect to these?

1. They only add a single nucleotide
2. They only add a string of nucleotides and not a single nucleotide
3. Terminal transferase adds a series of nucleotides at the 3’ end
4. Taq polymerase adds a single nucleotide at the 5’ end of the PCR product

✅ Correct Answer: 3

Which of the following statements is correct with respect to exonuclease?

1. They only act on single stranded DNA molecules
2. They only act on double stranded DNA molecules
3. They remove a single nucleotide base at a time
4. They remove nucleotide bases from the middle of a polynucleotide chain

✅ Correct Answer: 3

How many approaches are there which can be used for exonucleolytic activity in double stranded DNA molecules?

1. 1
2. 2
3. 3
4. 4

✅ Correct Answer: 2

What is the mode of action of exonuclease III?

1. Exonuclease III acts on single stranded DNA in 3’-5’ direction
2. Exonuclease III acts on double stranded DNA in 5’-3’ direction
3. Exonuclease III acts on single stranded DNA in 5’-3’ direction
4. Exonuclease III acts on double stranded DNA in 3’-5’ direction

✅ Correct Answer: 4

Which of the following statements is correct regarding S1 nuclease?

1. It acts on double stranded DNA
2. It acts on single stranded DNA
3. It acts on both types of strands
4. It is obtained from E. coli

✅ Correct Answer: 2

What happens if a DNA molecule is treated by first Exonuclease III and then followed by treatment with S1 nuclease?

1. The molecule is shortened only from 3’ end
2. The molecule is shortened only from 5’ end
3. The molecule is shortened from both the ends
4. Only Exonuclease acts and S1 doesn’t acts

✅ Correct Answer: 3

How can one end be protected from the action of Exonuclease III, so that the molecule is not shortened from both the ends?

1. By using Phosphorothioate nucleotide analogue
2. By making both the ends double stranded in nature
3. By labelling one end with a radioactive compound
4. By increasing the time of exposure of the DNA molecule to the enzyme

✅ Correct Answer: 1

Bal31 is also an enzyme which is used. Which of the following statements hold true in its context?

1. It is having only 3’-5’ exonuclease activity and no endonuclease activity
2. It is having only an endonuclease activity
3. It is having 5’-3’ exonuclease activity
4. It leads to shortening from both the ends

✅ Correct Answer: 4

The extent of deletions can be manipulated by controlling which of them?

1. Time of incubation only
2. Amount of nuclease added
3. They both have a role to play in the extent of the deletion
4. 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

✅ Correct Answer: 3

What is the function of methylase?

1. Addition of methyl groups to DNA
2. Removal of methyl groups from DNA
3. Both in removal and addition of methyl groups from DNA
4. It is used in production of methane gas

✅ Correct Answer: 1

Ligation is defined as ______________

1. Alignment of only double stranded DNA molecules at the ends and the formation of phosphodiester bonds between both the strands
2. Alignment of either of the double or single stranded DNA molecules and formation of glycosidic bonds between both the strands
3. 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
4. Alignment of single stranded DNA molecules and formation of glycosidic bonds between these strands

✅ Correct Answer: 3

If only one bond is broken in the sugar-phosphate backbone, it is called as ___________

1. gap
2. nick
3. break
4. leakage

✅ Correct Answer: 2

How many categories of ligation reaction are there on the basis of ends created?

1. 1
2. 2
3. 3
4. 4

✅ Correct Answer: 2

In the case of blunt-end ligation, blunt ends can be generated by ___________

1. simply the action of restriction endonuclease which gives straight ends
2. the polishing of staggered ends
3. both the action of restriction endonuclease which gives straight ends and polishing of staggered ends
4. by the action of restriction endonuclease which gives staggered ends

✅ Correct Answer: 3

The ligation reaction is more efficient in which case?

1. Blunt end ligation
2. Sticky end ligation
3. Both have the same efficiency
4. Depends on the reaction conditions

✅ Correct Answer: 2

The sticky ends are held together by which type of bonds?

1. Hydrogen bond
2. Covalent bond
3. Ionic bond
4. Van-der-waal forces

✅ Correct Answer: 1

Why sticky ended ligations are carried out at temperatures lower than room temperature?

1. 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
2. The energy required to break the bonds holding the ends is very less than that of the kinetic and vibrational energy at room temperature
3. The enzyme carrying out ligation is unstable at low temperature
4. The sticky ends created, don’t just relegate at low temperature

✅ Correct Answer: 1

If a ligation reaction is being carried out and recircularization is observed, which type of reaction is being carried out?

1. Intramolecular
2. Intermolecular
3. Both observe recircularization equally
4. Recirculation is not possible in any of the cases

✅ Correct Answer: 1

What is the kinetics of the intramolecular and intermolecular ligation reactions?

1. Second order kinetics for intramolecular and first order for intermolecular
2. First order kinetics for intramolecular and second order for intermolecular
3. Both are first order
4. Both are second order

✅ Correct Answer: 2