Biotechnology and its Applications — NCERT Solutions

Cry proteins are insecticidal proteins produced by the bacterium Bacillus thuringiensis (Bt). Different cry genes produce toxins effective against specific insect groups. Humans have exploited this by cloning cry genes into crop plants to make Bt crops such as Bt cotton, Bt corn, etc., which are resistant to insect pests and reduce the need for insecticides.

Gene therapy is a method of treating a disease by inserting a normal functional gene into a person’s cells to compensate for a defective gene.

Example: ADA deficiency

• ADA deficiency is caused by deletion of the gene for adenosine deaminase.
• In the first clinical gene therapy, lymphocytes were taken from the patient and cultured outside the body.
• A functional ADA cDNA was introduced into these cells using a retroviral vector.
• The genetically modified lymphocytes were then returned to the patient.
• Since lymphocytes are not immortal, the patient needs periodic infusions.
• A more permanent cure may be possible if the functional gene is introduced into early embryonic cells or marrow cells producing ADA.

The experimental steps for cloning and expressing a human gene in E. coli are:

1. Isolate the gene for the desired human protein, e.g. growth hormone.
2. Cut both the human DNA fragment and a plasmid vector with the same restriction endonuclease.
3. Join the human gene to the plasmid using DNA ligase to make a recombinant plasmid.
4. Introduce the recombinant plasmid into E. coli by transformation.
5. Allow the bacterium to multiply.
6. The inserted gene is then expressed to produce the human protein.

A simple flow diagram is:
Human gene → restriction enzyme cutting → plasmid vector cut → ligation → recombinant plasmid → transformation into E. coli → cloning/expression → human growth hormone.

A method suggested by the chapter’s idea of rDNA technology is to introduce genes that block oil synthesis in the seed. By using gene silencing/RNA interference or related genetic modification, the enzymes needed for oil (hydrocarbon) formation can be prevented from being made, so the seed would accumulate much less oil. This uses the principle of manipulating genes to alter the chemical composition of the seed.

The chapter’s answer is that blood does not normally have proteases and nucleases because these enzymes would digest body proteins and nucleic acids. So the correct response is No.