Question

Recombinant DNA technology has uses of interest in the medical field. One is gene therapy to introduce a normal gene into cells containing a defective gene. The first authorized human gene therapy was given to a 4-year-old girl with severe combined immune deficiency (SCID) who had a defective gene for adenosine deaminase (ADA). A modified retrovirus was constructed to contain the human ADA gene which could be expressed in human cells without replication of the virus. Another clinical use for recombinant DNA technology is to have rapidly replicating bacteria produce large amounts of specific proteins, for example, human proteins such as hormones. Expression of a cukaryotic gene in prokaryotes involves A. a Shine-Delgarno (SD) sequence in mRNA. B. absence of introns. C. regulatory elements upstream of the gene. D. a fusion protein. E. all of the above.

Short answer

Answer: E. All of the above.

Step-by-step solution

Understanding the terms

Before we continue with the question, let's review each of the given options. - Shine-Dalgarno (SD) sequence: A ribosome binding site found in prokaryotic mRNA, crucial for translation initiation. - Intron absence: Introns are non-coding regions of a gene found in eukaryotic cells and are removed during mRNA splicing. - Regulatory elements upstream of the gene: These are DNA sequences located near the starting point of a gene, and they play a role in activating or repressing gene expression. - Fusion protein: A protein resulting from the combination of two or more genes, which are usually from different species. Now that we have a better comprehension of the terms, we can proceed to evaluate each option for its role in expressing a eukaryotic gene in prokaryotes.

Evaluating each option

A. A Shine-Delgarno (SD) sequence in mRNA: This sequence is essential for translation initiation in prokaryotic cells. Eukaryotic mRNAs do not have SD sequences, but it must be introduced for prokaryotic expression. B. Absence of introns: Eukaryotic genes typically contain introns, and prokaryotic cells do not have the machinery to remove them. The introns must be removed before expressing the eukaryotic gene in prokaryotes. C. Regulatory elements upstream of the gene: The regulatory elements in eukaryotic cells differ from those in prokaryotic cells. Eukaryotic regulatory elements need to be replaced with prokaryotic ones for proper gene expression. D. A fusion protein: While not always necessary, fusion proteins can be used to express eukaryotic genes in prokaryotes. This technique improves compatibility, solubility, or detection of the expressed eukaryotic protein.

Choosing the correct answer

All of the above options (A, B, C, and D) are components involved in the expression of a eukaryotic gene in prokaryotes. Hence, the correct answer is: E. All of the above.