Question

Bacteria protect themselves from viruses by fragmenting viral DNA with
(a)Endonuclease
(b)Exonuclease
(c)Gyrase
(d)Ligase

Answer 1

Hint Bacteria is a prokaryotic microorganism that consists of numerous shapes from spherical to spiral and appeared first on earth which inhabit soil, water, radioactive waste, acidic hot springs, and the deep biosphere.

Complete answer:
Bacteria protect themselves from viruses by fragmenting viral DNA with an endonuclease. The endonuclease is also known as restriction enzyme which is a protein that is produced by bacterial cells which leaves DNA at specific sites along with the molecule. The restriction enzyme cleaves foreign DNA in the bacterial cell and eliminates infecting organisms. Bacteria use a restriction enzyme to defend against the bacterial viruses which are known as bacteriophages or page is which infects a bacteria while inserting its DNA into the bacterial cell for replication. The replication is resisted by the restriction enzyme of the phage DNA by cutting it into many pieces. The name of the restriction enzyme is based on their ability to restrict or limit the number of strains of the bacteriophage which infect a bacteria. Endonucleases are the enzymes that cleave a phosphodiester bond in the polynucleotide chain and have no regard for sequence while cutting DNA and others at specific nucleotide sequences.

Additional information:
Exonuclease: They are the enzyme which works for cleaving nucleotides one at a time from a polynucleotide chain. The humans constitute a different type of endonuclease and are known to be essential for the proper processing of histone pre-mRNA which helps in directing the signal cleavage process. It continues the breakdown of the product until it is completely degraded and allows nucleotides to be recycled.
Gyrase: It is an enzyme that reduces the topological strain in an ATP. It causes negative supercoiling of the DNA and relaxes positive supercoils by looping the template to form a crossing and cutting one of the double helices for passing the other and releasing the break which changes the linking number in each enzymatic step.
Ligase: It is an enzyme that catalyzes the joining of two large molecules that are forming a new chemical bond with the hydrolysis of a small chemical group of the large molecules of two compounds that are linked together.

So, the correct answer is 'Endonuclease'.

Note: The length of the viral genome is 1,200,000 nucleotides which code for 900 proteins and the smallest known virus is the circovirus which is about 20 nanometres in diameter and the viral genome constitutes 1700 new nucleotides which code for two proteins.