Which of the following statements is not true about restriction enzyme?

It is isolated from viruses.

The correct answer is Option (2) –It is isolated from viruses.

The statement "It is isolated from viruses." is not true about restriction enzymes.

Restriction enzymes, also known as restriction endonucleases, are enzymes that recognize specific DNA sequences and cleave the DNA at those recognition sites. They are essential tools in molecular biology and genetic engineering, as they allow scientists to cut DNA at precise locations.

The correct characteristics of restriction enzymes are:

1. Restriction enzymes belong to a larger class of enzymes called nucleases. These are of two kinds; exonucleases and endonucleases. Exonucleases remove nucleotides from the ends of the DNA whereas, endonucleases make cuts at specific positions within the DNA.
2. Each restriction endonuclease functions by ‘inspecting’ the length of a DNA sequence. Once it finds its specific recognition sequence, it will bind to the DNA and cut each of the two strands of the double helix at specific points in their sugar -phosphate backbones. Each restriction endonuclease recognises a specific palindromic nucleotide sequences in the DNA.
3. When a restriction enzyme cleaves DNA, it creates either blunt ends (straight cuts with no overhangs) or sticky ends (overhanging ends with single-stranded DNA). Different restriction enzymes can produce different types of ends, and the same type of sticky ends can be generated in different DNA molecules if they have compatible recognition sequences.

However, restriction enzymes are not isolated from viruses. They are naturally occurring enzymes found in bacteria as a part of their defense mechanism against viral infections. Bacteria use restriction enzymes to cut and destroy the viral DNA that enters their cells, preventing the virus from replicating. Scientists have isolated and purified these enzymes for use in various applications, but they are not isolated from viruses themselves.