Question

Describe the composition and function of a typical CRISPR system of bacteria

Answer 1

CRISPR are segments of prokaryotic Deoxyribonucleic acid containing short repetitions of base sequences.Its function is a immune system of prokaryotes which confers resistance to elements (foreign genetic) such as phages and plasmids, & provides a form of acquired immunity in the organism.

CRISPR (Clsutered Regularly Interspaced Palindromic Repeats) is a defense mechanism,present in bacteria and archaea. which confers immunity against phages.All species of bacteria and archea are parasitized by viruses known as phages.Accordingly, prokaryotes have evolved many different types of protection against infection by phages and other source of foreign DNA.These include prevention of absorption,blocking of injection,abortive infection and the restriction modification system. CRISPR DNA sequences and their associated proteins are one such type of protection.The CRISPR system protects prokaryotic cells by destroying viral DNA after it has entered the cell.

Phages infect prokaryotic cells by binding the surface protein,injecting their DNA through cell wall,and conquer the cell protein machinary to replicate the DNA.If,for any reason,the DNA is destroyed before it can cause infection.Small fragments are integrated into characteristic loci(called CRISPR loci) within the cell genome. Later,if the cell encounters foreign DNA,it will compare it to the short stored sequence and foreign DNA matching ,after then the foreign DNA will be destroyed by enzymes.