Question

__________are the enzymes used for cutting the DNA molecule into fragments. An example for this type of enzyme is EcoRI. What do EcoR and Ecol stand for?

Answer 1

Hint:In the year 1963, the two enzymes responsible for restricting the growth of bacteriophage in E.coli were isolated. One of these added methyl groups to DNA (methylase), while the other cut DNA. The latter was called restriction endonuclease.

Complete answer:
Restriction enzymes serve as chemical knives to cut genes (= DNA) into defined fragments. These may then be used
(i) To determine the order of genes on chromosomes.
(ii) To analyse the chemical structure of genes and of regions of DNA which regulate the functions of genes. To create new combinations of genes.

Stanley Cohen and Herbert Boyer accomplished the process of gene encoding in 1972 by isolating the antibiotic resistance gene by cutting out a piece of DNA from a plasmid which was responsible for conferring antibiotic resistance.

The cutting and removing of DNA at specific significant locations became possible with the discovery of the so-called molecular scissors' - restriction enzymes. The enzymes which cut base pairs at different locations are called selectable marks. They generate a new DNA type or can be said as DNA recombinant.

The cut piece of DNA was linked with the plasmid DNA. These plasmid DNA act as vectors to transfer the piece of DNA attached to it into the host organism. The linking of gene that shows resistance to antibiotic such as penicillin with the plasmid vector became possible with the enzyme DNA ligase that joins two DNA segments EcoR and EcoI stands for "E" denotes and shows generic name which is "Escherichia" and "co" shows species name, "coli" – in this the R represents the particular strain, in this case RY13, and the last part of its name, the I, denotes that it was the first enzyme isolated from this strain.

Hence the correct answer is option ‘A’ i.e, restriction enzymes.

Note:The first restriction endonuclease - Hind II, whose functioning depended on a specific DNA nucleotide sequence was isolated and characterized five years later. It was found that Hind II always cut DNA molecules at a particular point by recognizing a specific sequence of six base pairs. This specific base sequence is known as the recognition sequence for Hind-II.