50. Which one among the following is a nuclease?
(a) DNase I
(b) Helicase
(c) Ligase
(d) Polymerase

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What is a Nuclease?

A nuclease is an enzyme responsible for cleaving the phosphodiester bonds between nucleotides in nucleic acids (DNA or RNA). These enzymes are involved in a variety of cellular processes, such as DNA repair, replication, and recombination.

Nucleases are divided into two main categories:

1. Exonucleases: These enzymes remove nucleotides from the ends of a DNA or RNA strand.

2. Endonucleases: These enzymes cleave the phosphodiester bond within the nucleic acid strand.

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Understanding the Options

Let’s break down the choices to determine which one is a nuclease:

• (a) DNase I: Correct Answer. DNase I is a nuclease enzyme that specifically cleaves DNA by breaking phosphodiester bonds between nucleotides, resulting in the fragmentation of DNA. It plays a role in DNA degradation, repair, and apoptosis.

• (b) Helicase: Incorrect. Helicases are enzymes that unwind the double-stranded DNA during processes like replication and transcription. They do not cleave nucleic acids, but rather separate the strands.

• (c) Ligase: Incorrect. Ligases are enzymes that join two strands of DNA or RNA by catalyzing the formation of a phosphodiester bond. They do not cleave nucleic acids; instead, they are involved in the repair of breaks in the DNA backbone.

• (d) Polymerase: Incorrect. Polymerases are enzymes that synthesize DNA or RNA by adding nucleotides to a growing strand. They do not break nucleic acids but rather help build them by elongating the chain.

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Conclusion

Among the listed options, DNase I is the correct answer as it is a nuclease enzyme that degrades DNA by breaking phosphodiester bonds.

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Correct Answer: (a) DNase I