Summary

This chapter brought together the two halves of biotechnology that the WBCHSE syllabus groups into a single Chapter 10: the underlying principle and process of recombinant DNA technology, and the major real-world applications this technology has enabled.

On the principle-and-process side, the chapter explained why DNA's chemical uniformity and the universality of the genetic code make it possible to move a gene between very different organisms; how restriction enzymes cut DNA at precise, palindromic recognition sequences, producing sticky or blunt ends; how cloning vectors such as the plasmid pBR322 -- with an origin of replication, selectable marker genes, and unique restriction sites -- carry a foreign gene into a host cell and allow it to be identified through insertional inactivation; how host cells are made competent to take up foreign DNA; and how the complete process moves from isolating and cutting DNA, through amplifying a target sequence using PCR (denaturation, annealing, extension, driven by heat-stable Taq polymerase), to ligating the insert into the vector with DNA ligase, transforming a host cell, selecting true recombinants, and finally purifying the product through downstream processing.

On the applications side, the chapter covered how this same underlying process has been put to use in human health -- producing genetically engineered human insulin (Humulin) by expressing the A and B chains separately in E. coli, producing safer recombinant subunit vaccines such as the Hepatitis B vaccine, enabling highly sensitive molecular diagnosis through PCR and ELISA, correcting genetic disorders through gene therapy (illustrated by ADA deficiency), and the emerging promise of stem cell therapy -- and in agriculture, through Bt crops such as Bt cotton, which use the Bacillus thuringiensis toxin gene to provide built-in, insect-specific pest resistance. It also covered transgenic animals, produced to study gene function and disease, to serve as bioreactors producing therapeutic proteins in milk, or to test vaccine safety. …