Question

How many major types of restriction endonucleases have been recognised?
a. One
b. Two
c. Three
d. Four

Answer 1

Restriction enzymes are the protein specifically endonuclease which is used to cleave the foreign DNA. They can cut DNA on specific locations, they are used In DNA replication, translation, and recombinant biotechnology. They cut the plasmid and help in eradicating the diseased or unwanted gene pairs.

Complete answer:
Four types of restriction enzymes are acknowledged which are named as one, two, three, and four in roman letters
- They differ in structure, cleavage site, specificity and cofactors.
- Methylase activities and addition of cap in transcription and replication which is very essential for the process to take place.
- DNA is cleaved at a specific site by type two endonucleases and other types of endonucleases are cleaved at non-specific sites.
- Restriction enzymes originate from a common ancestral protein and evolved to recognize specific sequences.
- Type 1 enzymes require ATP and S- adenosyl-L-methionine to properly work.
- Type2 enzymes require magnesium and are independent of methylase.
- Type 3 enzymes require ATP and are complex with a modification methylase.
- Type 4 enzymes target modified DNA.
- They are used to assist the insertion of genes into vectors during the process of gene cloning and protein production.
- They can be used to differentiate alleles by recognizing single base changes in DNA known as Single nucleotide polymorphisms (SNPs).

Hence, the correct answer is option (D).

Note: Discovery of the enzymes was done within the 1970s, many restriction enzymes were recognized; as an instance, more than 3500 specific Type II restriction enzymes have been characterized. Each enzyme is known as after the bacterium from which it turned into isolated, the usage of a naming machine based on the bacterial genus, species, and strain.