Question

Which of the following is correct about nucleases?

• A. It is a large class of enzymes consisting of exonucleases and endonucleases
• B. Exonucleases remove nucleotide from only one end of the DNA
• C. Endonucleases make specific cuts within the DNA by breaking ionic bonds
• D. All of them recognise palindromic nucleotide sequences in the DNA

Answer 1

The correct option is A It is a large class of enzymes consisting of exonucleases and endonucleases

Nucleases are a large class of enzymes that degrade DNA by breaking phosphodiester bonds between the nucleotides. Based on its site of action on DNA, they are divided into two types:

Exonuclease

• It removes nucleotides by breaking the phosphodiester bond
• It removes only one nucleotide at a time from either end of a DNA
• It is present in both prokaryotes and eukaryotes

Endonucleases

• It recognizes palindromic nucleotide sequences within the DNA molecule called recognition site and breaks phosphodiester bond at a particular nucleotide within the restriction site.
• It is present in prokaryotes and provides protection against invading bacteriophage DNA