By inserting eukaryotic genes into bacteria, a prokaryotic organism, human insulin, a protein hormone that controls blood sugar levels, and many other eukaryotic proteins can be mass-produced.
How would the expression of the insulin gene be affected if an unaltered human insulin gene was inserted into the DNA of a prokaryotic organism?
(A) Because prokaryotic cells lack mRNA processing, the insulin protein produced would be non-functional in humans.
(B) Because protein synthesis is identical in all living things, the insulin protein produced in the prokaryotic cell would be the same as it is in the eukaryotic cell.
(C) Prokaryotic cells would have different transcription but identical translation to eukaryotic cells, so there would be no difference between insulin produced in prokaryotic cells and insulin produced in eukaryotic cells.
(D) Because bacteria have smaller ribosomes, the rate of insulin production would be much higher, as would the accuracy of amino acid placement.
VerifiedHint: Consider the differences between prokaryotic and eukaryotic gene expression, specifically the steps involved in mRNA processing.
Complete step-by-step Answer: Prokaryotic cells, such as bacteria, lack the machinery for mRNA processing, which includes splicing and polyadenylation. Splicing removes introns, non-coding regions of the gene, from the mRNA transcript, while polyadenylation adds a tail of adenine nucleotides to the end of the mRNA.
In eukaryotes, mRNA processing ensures that the mature mRNA transcript contains only the exons, the coding regions of the gene, and the correct start and stop codons. This is crucial for proper translation into a functional protein.
If an unaltered gene for human insulin were inserted into a prokaryotic cell, the mRNA transcript would not undergo splicing or polyadenylation. This would result in an mRNA transcript that contains both exons and introns, as well as an incomplete polyadenylation signal.
As a consequence, the ribosomes in the prokaryotic cell would read through the introns and translate them into amino acids, leading to the production of a non-functional insulin protein. The extra amino acids from the introns would disrupt the structure and function of the insulin molecule, rendering it unable to regulate blood sugar levels effectively.
Hence the correct answer is Option A
Note: The production of recombinant proteins in prokaryotic organisms has revolutionized the pharmaceutical industry, allowing for the mass production of important therapeutic proteins like insulin. However, as this question highlights, there are limitations to using prokaryotic expression systems for eukaryotic proteins.
