● The construction of the `color{Violet}"first recombinant DNA"` emerged from the possibility of linking a gene encoding antibiotic resistance with a `color{Brown}"native plasmid"` (autonomously replicating circular extra-chromosomal DNA) of `color{Violet}"𝘚𝘢𝘭𝘮𝘰𝘯𝘦𝘭𝘭𝘢 𝘵𝘺𝘱𝘩𝘪𝘮𝘶𝘳𝘪𝘶𝘮"`.
● `color{Brown}"Stanley Cohen"` and `color{Brown}"Herbert Boyer"` accomplished this in 1972 by isolating the `color{Violet}"antibiotic resistance gene"` by cutting out a piece of DNA from a plasmid which was responsible for `color{Violet}"conferring antibiotic resistance"`.
● The `color{Violet}"cutting of DNA"` at specific locations became possible with the discovery of the so-called `color{Violet}"molecular scissors"`– `color{Brown}"restriction enzymes"`.
● The `color{Violet}"cut piece"` of DNA was then `color{Violet}"linked"` with the `color{Violet}"plasmid DNA"`.
● These plasmid DNA act as `color{Violet}"vectors to transfer"` the piece of DNA attached to it.
● In the same way as a `color{Violet}"mosquito"` acts as an insect vector to transfer the `color{Violet}"malarial parasite"` into human bod, a `color{Violet}"plasmid"` can be used as vector to deliver an `color{Violet}"alien piece of DNA"` into the host organism.
● The `color{Violet}"linking"` of antibiotic resistance gene with the plasmid vector became possible with the `color{Brown}"enzyme DNA ligase"`, which acts on cut DNA molecules and `color{Violet}"joins their ends"`.
● This makes a `color{Violet}"new combination"` of `color{Violet}"circular autonomously"` `color{Violet}"replicating DNA"` created in vitro and is known as `color{Brown}"recombinant DNA"`.
● When this DNA is transferred into `color{Violet}"𝘌𝘴𝘤𝘩𝘦𝘳𝘪𝘤𝘩𝘪𝘢 𝘤𝘰𝘭𝘪"`, a bacterium closely related to `color{Violet}"𝘚𝘢𝘭𝘮𝘰𝘯𝘦𝘭𝘭𝘢"`, it could replicate using the new `color{Violet}"host’s DNA polymeras"`e enzyme and make multiple copies.
● The ability to `color{Violet}"multiply copies"` of antibiotic resistance gene in E. coli was called `color{Violet}"cloning of"` `color{Violet}"antibiotic resistance"` gene in E. coli.
● Thus it can be inferred that there are `color{Violet}"three basic steps"` in genetically modifying an organism —
(i) `color{Violet}"Identification"` of DNA with desirable genes;
(ii) `color{Violet}"Introduction"` of the identified DNA into the host;
(iii) `color{Violet}"Maintenance"` of introduced DNA in the host and transfer of the DNA to its progeny.
● The construction of the `color{Violet}"first recombinant DNA"` emerged from the possibility of linking a gene encoding antibiotic resistance with a `color{Brown}"native plasmid"` (autonomously replicating circular extra-chromosomal DNA) of `color{Violet}"𝘚𝘢𝘭𝘮𝘰𝘯𝘦𝘭𝘭𝘢 𝘵𝘺𝘱𝘩𝘪𝘮𝘶𝘳𝘪𝘶𝘮"`.
● `color{Brown}"Stanley Cohen"` and `color{Brown}"Herbert Boyer"` accomplished this in 1972 by isolating the `color{Violet}"antibiotic resistance gene"` by cutting out a piece of DNA from a plasmid which was responsible for `color{Violet}"conferring antibiotic resistance"`.
● The `color{Violet}"cutting of DNA"` at specific locations became possible with the discovery of the so-called `color{Violet}"molecular scissors"`– `color{Brown}"restriction enzymes"`.
● The `color{Violet}"cut piece"` of DNA was then `color{Violet}"linked"` with the `color{Violet}"plasmid DNA"`.
● These plasmid DNA act as `color{Violet}"vectors to transfer"` the piece of DNA attached to it.
● In the same way as a `color{Violet}"mosquito"` acts as an insect vector to transfer the `color{Violet}"malarial parasite"` into human bod, a `color{Violet}"plasmid"` can be used as vector to deliver an `color{Violet}"alien piece of DNA"` into the host organism.
● The `color{Violet}"linking"` of antibiotic resistance gene with the plasmid vector became possible with the `color{Brown}"enzyme DNA ligase"`, which acts on cut DNA molecules and `color{Violet}"joins their ends"`.
● This makes a `color{Violet}"new combination"` of `color{Violet}"circular autonomously"` `color{Violet}"replicating DNA"` created in vitro and is known as `color{Brown}"recombinant DNA"`.
● When this DNA is transferred into `color{Violet}"𝘌𝘴𝘤𝘩𝘦𝘳𝘪𝘤𝘩𝘪𝘢 𝘤𝘰𝘭𝘪"`, a bacterium closely related to `color{Violet}"𝘚𝘢𝘭𝘮𝘰𝘯𝘦𝘭𝘭𝘢"`, it could replicate using the new `color{Violet}"host’s DNA polymeras"`e enzyme and make multiple copies.
● The ability to `color{Violet}"multiply copies"` of antibiotic resistance gene in E. coli was called `color{Violet}"cloning of"` `color{Violet}"antibiotic resistance"` gene in E. coli.
● Thus it can be inferred that there are `color{Violet}"three basic steps"` in genetically modifying an organism —
(i) `color{Violet}"Identification"` of DNA with desirable genes;
(ii) `color{Violet}"Introduction"` of the identified DNA into the host;
(iii) `color{Violet}"Maintenance"` of introduced DNA in the host and transfer of the DNA to its progeny.