Question

Tom was trying to isolate a human gene (X) responsible for producing an enzyme (Y). His target was to synthesize Y on a large scale for commercial utility. Mention the correct order of the steps that he needs to perform in order to isolate his gene of interest.
I. Obtaining cell sample from desired tissue
II. Separation of desired DNA by gel electrophoresis
III. Cell lysis
IV. Amplification of desired DNA sequence by PCR
V. Isolation of genomic DNA
VI. Identification of desired band, cutting and elution of DNA from gel

• A. I → II → V → VI → III → IV
• B. I → III → V → II → IV → VI
• C. I → III → V → IV → II → VI
• D. I → III → IV → V → II → VI

Answer 1

The correct option is C I → III → V → IV → II → VI

The isolation of the gene of interest from the genome can be done by the following steps:

• The desired tissue or site is selected from where the cells are scraped out.
• This is followed by cell lysis which releases all the components within it in the medium.
• This is followed by isolation of genomic DNA.
• The desired sequence in the DNA is amplified using polymerase chain reaction with specific primers.
• The desired DNA fragments are separated by gel electrophoresis according to their size.
• Finally, the band obtaining the desired DNA sequence/gene of interest is identified by comparing it to the DNA ladder (a solution of DNA of different lengths used as a reference to predict the size of unknown DNA molecules).
• The region containing the gene of interest is excised out of the gel block.
• The gel slice is then treated with solvents and buffers to get the sequence with gene of interest.

Hence, the correct sequence of events is: I → III → V → IV → II → VI