BIOTECHNOLOGY : PRINCIPLES AND PROCESSES
Read the following passage carefully and answer the given questions.
Biotechnology deals with large scale production and marketing of products and processes using live organisms, cells or enzymes. Modern biotechnology using genetically modified organisms was made possible only when man learnt to alter the chemistry of DNA and construct recombinant DNA. This key process is called recombinant DNA technology or genetic engineering. This process involves the use of enzymes, viral vectors to carry the foreign DNA into host organisms, expression of the foreign gene, purification of the gene product, and finally making a suitable formulation for marketing. Restriction endonucleases are used in genetic engineering to form ‘recombinant’ molecules of DNA, which are composed of DNA from different sources/genomes. Gene cloning allows us to isolate and introduce only one or a set of desirable genes without introducing undesirable genes into the target organism. The ability to multiply copies of antibiotic resistance gene in E. coli was called cloning of antibiotic resistance gene in E. coli. In PCR, multiple copies of the gene (or DNA) of interest is synthesised in vitro using two sets of primers (small chemically synthesised oligonucleotides that are complementary to the regions of DNA) and the enzyme DNA polymerase.
The first restriction endonuclease enzyme was:
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → Hind II
A restriction endonuclease is an enzyme that cuts DNA at a specific base sequence. The first one to be isolated and characterised was Hind II. It was found that it always cuts DNA at a particular point, by recognising a specific sequence of six base pairs, called its recognition sequence.
The name of such an enzyme follows a convention. The first letter is from the genus and the next two letters are from the species of the bacterium it came from. A roman number shows the order in which the enzymes were isolated from that strain.
(1) Bam H I — Incorrect. It is a restriction enzyme, but not the first one. It comes from Bacillus amyloliquefaciens.
(2) Hind II — Correct. It was the first restriction endonuclease that depended on a specific DNA sequence.
(3) Eco R I — Incorrect. It is a restriction enzyme from Escherichia coli RY 13. The letter R comes from the strain.
(4) Hind III — Incorrect. It is another enzyme from the same bacterium as Hind II. The number III shows that it was isolated later.
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NCERT Extract:
Restriction Enzymes –
