Many useful products, mainly for medical purposes, are produced by cloning human genes into other organisms, which then mass-produce these compounds. Which of the following organisms has NOT been used to mass-produce pharmaceutical compounds used to treat human diseases? (ebook Module 12.6)

A. Escherichia coli

B. mice

C. Saccharomyces cerevisiae

D. pigs

The correct answer is : A.

Explanation:

This is because of the following reasons: Escherichia coli is a bacteria and hence is a prokaryote. The cloning of human (eukaryote) genes is done to obtain in-vitro protein expression which are to be used a pharmaceutical compounds. Although the phenomenon of Central Dogma takes place in both Prokaryotes and Eukaryotes, the mechanism is very different. Some of the differences includes: Eukaryotic genes contain certain non-protein encoding sequences called the Intron sequences which needs to be removed from the transcribed mature mRNA by Spliceosome. This phenomenon is absent in prokaryotes as they do not possess introns. Hence, proper processing of eukaryotic mRNA is not possible in prokaryotes. The mature eukaryotic mRNA has a 5' cap and 3' polyadenylated tail which is added by a capping enzyme and a poly-A polymerase enzyme to increase their stability. This will not be possible in a prokaryote as they lack these enzymes. The translation of membrane proteins and secretory proteins is carried on by the ribosomes bound to the endoplasmic reticulum. This structure is absent in prokaryotes, hence they will be unable to produce a proper polypeptide sequence. Finally, the eukaryotic proteins undergo various modifications after formation, like methylation, acetylation, etc. These reactions cannot be carried out in a prokaryote as they lack the respective enzymes. Hence, we see a properly folded functional eukaryotic protein cannot be produced in a prokaryote.