Question

The figure above illustrates gene expression in prokaryotic and eukaryotic cells:
Human insulin, a protein hormone that controls blood sugar levels, and many other eukaryotic proteins can be mass-produced by inserting eukaryotic genes into bacteria.
If an unaltered gene for human insulin was inserted into the DNA of a bacteria cell, how would the expression of the insulin gene be affected?

• A. The insulin protein produced in the prokaryotic cell would be non-functional in humans because it would contain extra amino acids due to a lack of mRNA processing in prokaryotic cells.
• B. The insulin protein produced in the prokaryotic cell would be the same is it is in eukaryotic cells because protein synthesis is identical in all living things.
• C. Transcription would be different in prokaryotic cells, but the translation would be identical to eukaryotic cells, so there would be no differences between insulin produced in prokaryotic cells and insulin produced in eukaryotic cells.
• D. Since bacteria have smaller ribosomes, the rate of insulin production would be much higher, and the accuracy of amino acid placement would be much better.

Answer 1

The correct option is A The insulin protein produced in the prokaryotic cell would be non-functional in humans because it would contain extra amino acids due to a lack of mRNA processing in prokaryotic cells.

Human insulin preparation: Insulin gene is synthesized artificially and inserted into the bacterial plasmid forming a recombinant plasmid. The recombinant plasmid is re-inserted into the bacterial cells and the insulin gene is expressed when the bacteria undergo translation(a process which converts RNA to protein). In this manner, large quantities of bacterial cells are cultured in the bioreactors and then purified to get the final product.

When the insulin gene is artificially synthesized to be inserted into the bacterial plasmid, all the non-functional coding regions are pre-removed as the prokaryotic cell (bacteria) does not have the m-RNA processing mechanism. So, if the unaltered insulin(where the non-coding regions are not removed) is inserted into the bacteria, the insulin produced would be non-functional as it would contain extra amino acids from the non-coding regions.

So, the correct answer is option A.