Genetic Engineering: Overview

Introduction | Overall Laboratory Schedule | Required Reading | Genetic Engineering Table of Contents

Introduction

Recombinant DNA technology is a collection of techniques, including DNA cloning, that allows molecular biologists to analyze and manipulate the genetic material. Prior to DNA cloning it was virtually impossible to isolate and study individual genes of higher organisms. With the advent of recombinant DNA technology, however, genes can now be isolated from a complex genome relatively easily and analyzed in great detail. This ability has allowed us to undertake one of the most ambitious scientific projects of our time, the Human Genome Project, whose goal is to ultimately sequence the approximately 100,000 human genes (see Russell's Genetics, 5th ed., p. 486).

Recombinant DNA technology also allows an isolated gene to be manipulated, or engineered, in the test tube and then reintroduced into living organisms (see Russell, p. 448). Genetic engineering typically uses restriction enzymes to cut cloned genes at specific sites. The resulting DNA fragments can then be joined to other DNA fragments to produce a recombinant DNA molecule.

Among its many uses, genetic engineering can be used to produce large quantities of a normally rare protein. For example, human insulin and growth hormone, which are of great medical importance, have been purified in large amounts from bacterial cells expressing appropriately engineered genes (see Russell, p. 490). In addition, genetic engineering can be used to investigate basic questions in biology, such as when and where a gene is expressed (transcribed) during development.

More Information on the Uses of Genetic Engineering:

• To produce large amounts of a protein
• To analyze the expression pattern of a gene during development

Overall Laboratory Schedule

Over the next three laboratory periods, we will engineer a novel plasmid using some standard recombinant DNA techniques. A jointly prepared laboratory report describing your findings will be due one week after the final laboratory session. A timetable for each laboratory period follows:

• Week 1
  • Restriction digest recombinant plasmids
  • Analyze restriction digests by agarose gel electrophoresis
• Week 2
  • Isolate the desired restriction fragment of each plasmid.
  • Join the two desired fragments together.
  • Transform the ligation mixture into host cells.
• Week 3
  • Isolate plasmid DNA from transformed colonies.
  • Analyze plasmid DNA by agarose gel electrophoresis.
• Week 4
  • Laboratory report due (joint or individual)

Required Reading

From Russell's Genetics, 5th ed:

• "Gene Cloning," pp. 448 - 458
• "Restriction Enzyme Analysis of Cloned DNA Sequences," pp. 469 - 470

• Overview
• Directions for Laboratory Period 1
• How to Interpret the Results of the Restriction Enzyme Analysis
• Directions for Laboratory Period 2
• The Alkaline Lysis Procedure for Preparing Plasmid DNA
• Directions for Laboratory Period 3

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William R. Morgan wmorgan@acs.wooster.edu