recap

18.5 recap

Expression vectors maximize the expression of transgenes inserted into host cells. Biotechnology has been used to produce medicines and to develop transgenic plants with improved agricultural and nutritional characteristics.

learning outcomes

You should be able to:

  • Describe the essential features of expression vectors.

  • Summarize the advantages of modern recombinant DNA technology over selective breeding in agriculture.

  • Evaluate the ethical and environmental concerns posed by specific uses of biotechnology, taking into account the risks and rewards that would likely come from their use.

Question 1

What are the essential features of expression vectors?

Expression vectors have restriction site(s) for insertion of genes, a DNA replication origin, a tissue-specific active promoter for the proposed host cell, and often a sequence for signaling the protein to be sent to the extracellular medium for isolation in the lab.

Question 2

Compared with traditional methods, what are the advantages of using biotechnology for plant breeding?

Biotechnology is faster (one instead of many generations of breeding) and specific (only a single gene is introduced, instead of many during selection for a complex characteristic).

Question 3

After Cohen and Boyer did their experiment (see Key Concept 18.1), a group of scientists, public health officials, and bioethicists held a conference and agreed to a temporary moratorium on most recombinant DNA research. What do you think were the concerns that led to the moratorium? How was safety assured so that the moratorium was lifted?

Because the bacterium E. coli normally lives in the human intestine, there was a danger that lab strains resistant to multiple antibiotics might infect people. Furthermore, there may have been concern that the genes of antibiotic-resistant strains might recombine with the genes of normal strains, resulting in the development of multiple-antibiotic-resistant strains. Another concern was that bacteria could be used to harbor genes encoding toxins as biological warfare agents. To alleviate these concerns, the host E. coli strains were developed with multiple mutations so that they would require a special lab environment to survive. For example, mutations in genes for the synthesis for vital metabolites were introduced so the bacteria would need to be supplied with metabolites that the human intestine does not provide.