This set of Agricultural Biotechnology Multiple Choice Questions & Answers (MCQs) focuses on “Genetic Engineering Enzymes – Ligases”.
1. Joining of DNA fragments is called recombinant DNA.
a) True
b) False
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Explanation: Although cutting DNA precisely is very useful for DNA analysis, its full potential is only revealed when the fragments produced are joined together to give a new structure called as recombinant DNA.
2. At which stage is the enzyme isolated from bacteria?
a) T1 stage
b) T2 stage
c) T3 stage
d) T4 stage
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Explanation: The joining or ligation is achieved by the use of a DNA ligase enzyme. The most common ligase is isolated from the bacterial virus (T4 phage).
3. ________ is a group of enzyme which mediate annealing, sealing or joining of DNA fragments.
a) Protease
b) Ligase
c) Cellulase
d) Ribonuclease
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Explanation: DNA ligase is a group of enzyme which mediate annealing, sealing or joining of DNA fragments. Primarily, these enzymes are involved in the repair of DNA where sealing or union of DNA fragments takes place.
4. Ligases also help in process like DNA replication.
a) True
b) False
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Explanation: DNA ligases also play active part in processes like DNA replication and recombination. These enzymes are widely used in genetic engineering for the production of hybrid DNA.
5. Covalent bond is formed between the ______
a) 5ˈ phosphoryl and 3ˈ hydroxyl
b) 5ˈ hydroxyl and 3ˈ phosphoryl
c) 5ˈ phosphoryl and 5ˈ hydroxyl
d) 3ˈ phosphoryl and 3ˈ hydroxyl
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Explanation: The pairings are transient, owing to the weakness of hydrogen bonding between the few bases in the sticky ends but they can be stabilized by the use of DNA ligase which forms a covalent bond between the 5ˈ phosphoryl and 3ˈ hydroxyl.
6. Which of these enzymes help in end to end joining of DNA duplexes?
a) Cellulase
b) Ribonuclease
c) Ligase
d) T4 polynucleotide ligase
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Explanation: T4 polynucleotide ligase catalyses the end to end joining of DNA duplexes at the base paired end. This reaction could occur intermolecularly or intramolecularly.
7. Which of the following enzymes is used to remove incompatible sticky ends?
a) T4 polynucleotide ligase
b) S1 nuclease
c) Cellulase
d) Ribonuclease
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Explanation: Blunt ended ligation is a very useful form of joining together DNA fragments which have not been produced by the same restriction enzyme and which probably have incompatible sticky ends.
8. What is the molecular weight of enzyme isolated from E.coli?
a) 50 kDa
b) 75 kDa
c) 100 kDa
d) 1250 kDa
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Explanation: DNA ligases are isolated from E.coli and phage T4. The enzyme isolated from E.coli is a polypeptide chain with a molecular weight of 75 kDa.
9. What is the molecular weight of enzyme isolated from T4 bacteriophage?
a) 65 kDa
b) 68 kDa
c) 72 kDa
d) 76 kDa
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Explanation: The enzyme isolated from E.coli is a polypeptide chain and needs NAD+ as a cofactor. The ligase obtained from T4 bacteriophage is 68 kDa. It requires ATP as a cofactor and a source of energy.
10. Which of the following process don’t need ligases?
a) Joining process
b) Inserting recombinant DNA
c) Ligation of linkers
d) Label 5ˈ-termini
View Answer
Explanation: DNA ligases play an important role in genetic engineering. In the absence of DNA ligases recombinant DNA technology can never exist.
Sanfoundry Global Education & Learning Series – Agricultural Biotechnology
To practice all areas of Agricultural Biotechnology, here is complete set of 1000+ Multiple Choice Questions and Answers.
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