Question

The cutting of DNA at specific locations became possible with the discovery of
(A) Restriction enzymes
(B) Probes
(C) Selectable markers
(D) Ligases

Answer 1

Hint: An endonuclease enzyme plays a very important role in cutting DNA molecules into fragments. The machinery was first accepted in 1978 and the scientist got a Nobel prize for this discovery.

Complete step by step answer:
Let’s discuss the options and find the correct answer.
- Restriction enzymes rather called restriction endonuclease enzyme is a specific type of enzyme that can cleave into DNA molecules and cut at specific recognition sites. Thus it breaks the phosphodiester bond of DNA molecules. Depending on their ability to recognise the restriction site, restriction enzymes are of 4 types such as type-I, type-II, type-III and type-IV restriction enzymes.
- A probe is defined as a fragment of RNA or DNA with variable length that can detect the presence or absence of any nucleotide substances in the given sequence. It is a very important term in molecular biology techniques.
- Selectable markers are defined as a gene which can be inserted into bacterium or other cells in a culture medium. It results in a successful artificial selection process.
- DNA ligase is referred to as a specific enzyme that can catalyze the making of phosphodiester bonds at 3’ hydroxyl group and 5’phosphate group thus helps in joining DNA strands. This enzyme is also used in joining the okazaki fragments formed during DNA replication.
Hence option A: Restriction enzymes is the correct answer.

Note: There are several other endonuclease enzymes that are present in cells or used in molecular biology. These are S1 nuclease, Dnase, micrococcal nuclease etc. Their functions also differ with each other.