Biology · Biotechnology: Principles and Processes · NEET
NCERT lists exactly three basic steps in genetically modifying an organism: (i) identification of DNA with the desirable gene, (ii) introduction (insertion) of this DNA into the host, and (iii) maintenance of the introduced DNA in the host and transfer of the DNA to its progeny. A short way to remember: identify the gene, insert it, and maintain it. Learn them in this order because NEET often asks the sequence.
No, and mixing them up is the most common mistake. The three basic steps are the broad idea (identify, insert, maintain). The processes of recombinant DNA technology are the detailed lab steps: isolation of DNA, cutting DNA with restriction enzymes, amplification using PCR, ligation into a vector, insertion into the host, and getting the gene product with downstream processing. The processes are the 'how'; the three basic steps are the 'what'.
No. PCR (making many copies of the gene) is part of the detailed processes of recombinant DNA technology, not one of the three broad basic steps. The three basic steps are only identify, insert, and maintain. PCR fits inside the first idea (getting enough of the desired DNA) but NCERT never lists it as one of the three basic steps. NEET has asked PCR separately, so keep them apart.
A single copy of a gene is too little to work with. When the recombinant DNA is put into a host like E. coli, the host's own machinery (DNA polymerase) copies the DNA every time the host divides, giving multiple copies. This is called cloning. The host also lets the gene make its protein product. So the third basic step, maintenance in the host, is what turns one gene into many copies and a usable product.
Free DNA cannot easily enter a cell or replicate on its own inside a bacterium. A vector, usually a plasmid, carries the desired DNA into the host and has an origin of replication (ori) so the DNA can copy itself there. NCERT compares the plasmid vector to a mosquito that carries the malarial parasite into the human body. Without a vector, the introduced DNA would be lost.
Main steps in the formation of Recombinant DNA are given below. Arrange these steps in a correct sequence. A. Insertion of recombinant DNA into the host cell. B. Cutting of DNA at specific location by restriction enzyme. C. Isolation of desired DNA fragment. D. Amplification of gene of interest using PCR.
Try the real previous-year questions from this chapter — each with the answer and a full solution.
Identify and isolate the desired DNA, insert it into a host using a vector, and maintain the DNA in the host so it copies and makes its product.
Stanley Cohen and Herbert Boyer in 1972 made the first recombinant DNA by joining an antibiotic-resistance gene to a plasmid vector, then transferring it into E. coli where it multiplied.
DNA ligase joins the cut DNA fragment to the vector, forming a new circular recombinant DNA molecule.
Cloning is the result of the third step: once the recombinant DNA is inside a host, the host divides and makes many identical copies of the DNA, which is cloning.
Yes. NEET has directly asked students to arrange these steps in the correct sequence (NEET 2023), so learn the order: identify, insert, maintain.
