Which of the following are correct with reference to rDNA technology?

(A) Exo-nuclease removes nucleotides from the ends of DNA
(B) Replication starts at ori
(C) High velocity microparticle of gold, coated with DNA, are used to transfer DNA in animal a method known as gene gun
(D) Endo-nuclease makes cut at specific positions within DNA

Choose the correct answer from the options given below.

(A), (B) and (D) only

The correct answer is Option (1) → (A), (B) and (D) only 

The cutting of DNA at specific locations became possible with the discovery of the so-called ‘molecular scissors’– restriction enzymes. Restriction enzymes belong to a larger class of enzymes called nucleases. These are of two kinds :exonuclease and endonuclease . Exonuclease remove nucleotides from the ends of the DNA whereas, endonucleases make cuts at specific positions within the DNA.

Origin of replication (ori) is a sequence from where replication starts and any piece of DNA when linked to this sequence can be made to replicate within the host cells.

A method suitable for plants, cells are bombarded with high velocity micro-particles of gold or tungsten coated with DNA in a method known as biolistics or gene gun.