write the brief note on restriction endonucleases
Answers
Explanation:
A bacterium uses a restriction enzyme to defend against bacterial viruses called bacteriophages, or phages. When a phage infects a bacterium, it inserts its DNA into the bacterial cell so that it might be replicated. The restriction enzyme prevents replication of the phage DNA by cutting it into many pieces. Restriction enzymes were named for their ability to restrict, or limit, the number of strains of bacteriophage that can infect a bacterium.
Each restriction enzyme recognizes a short, specific sequence of nucleotide bases (the four basic chemical subunits of the linear double-stranded DNA molecule—adenine, cytosine, thymine, and guanine). These regions are called recognition sequences, or recognition sites, and are randomly distributed throughout the DNA. Different bacterial species make restriction enzymes that recognize different nucleotide sequences
Answer:
restriction endonucleases are the enzymes that make cuts at specific positions within the DNA these enzymes do not leave the ends and involve only one strand of the DNA duplex. Restriction endonucleases were found by Arber in 1962 in bacteria. They act as molecular Scissors.
They recognize the specific base sequence at palindrome sites in DNA duplex and cut its strands. For example, restriction endonuclease EcoRI found in the colon bacteria E. coli reocgnizes the base sequence GAATTC in DNA duplex and cuts its strands between G and A.
There are 3 types of restriction endonucleases :
1. Type I restriction endonucleases
2. Type II restriction endonucleases
3. Type III restriction endonucleases