Question

Which of the following statements does not hold true for restriction enzymes?
A. It recognises a palindromic nucleotide sequence
B. It is an endonuclease
C. It is isolated from viruses
D. It produces the same kind of sticky ends in different DNA molecules

Answer 1

Restriction Enzyme - A restriction enzyme or restriction endonuclease is an enzyme that cleaves DNA into fragments at or near specific sites within molecules known as restriction sites.
Restriction enzymes are one class of the vast endonuclease group of enzymes.
Restriction enzymes or restriction endonuclease are usually classified into four types on the basis of subunits. These are composition, cleavage position, sequence specificity and cofactor requirements.

Complete answer:
The restriction enzymes or restriction endonuclease are called molecular scissors and they are responsible for cutting DNA on specific sites.
They can be found in bacteria which provide a type of defence mechanism called the restriction modification system and the so-called process consists of two component restriction enzymes and modification enzymes.
The first component or restriction enzymes include restriction endonuclease which finds the presented foreign DNA and cuts it into process. Same kind of sticky end in separate distinct molecules of DNA are also created by these molecular scissors. Special sequence in the DNA recognised by restriction endonuclease or restriction enzymes is called palindromic nucleotide sequence.

Note:
The invention of restriction enzymes started with a hypothesis. In the 1960s, Werner Arber experienced a dramatic change in the bacteriophage DNA after it invaded these unaffected strains of bacteria: the DNA was degraded and cut into pieces.
Restriction enzymes or restriction endonucleases are used to cut DNA into smaller fragments in the laboratory. Always the cuts are made at specific nucleotide sequences. Different restriction endonucleases recognise and cut different DNA sequences.
The restriction enzyme or restriction endonuclease HsaI from the embryos of human or Homo sapiens has been isolated with both the tissue extract and nuclear extract. It proves not to be an usual enzyme, obviously related functionally to Type II endonuclease.