Gene Cloning Requires Knowledge of the Gene’s Unique Characteristics.
Organisms are loaded with DNA. Thousands of genes all exist together in the cell and each gene is made up of nucleotides. The gene cloner does not have a microscopic instrument that can pull one desired gene out of a cell. Before a gene cloner can hope to have many copies of their gene they need to have a plan for finding that gene. This means that they must have some information about the unique characteristics of the gene of interest. We will describe how this information can be used to identify the gene they wish to clone.
Fig. 3: Genes encode proteins and are a part of the chromosome. (Image by D. Lee)
“Traditional” Gene Cloning:
When a geneticist says they have a clone of a gene, it often means that they have a colony of bacteria that are all making many copies of that gene. How does one get bacteria to make copies of a gene that originated in a plant or animal?
Playing “tricks” on E. coli
In most cases, genes are cloned by playing a “trick” on an E. coli bacteria cell. Strains of these bacteria can be selected for their ability to grow rapidly in liquid nutrient media or on media agar plates but not in more natural environments (like your intestines where “wild” strains of these bacteria will grow). The lab strains become biological gene cloning factories if the gene cloner can give the bacteria a good reason to make copies of the new gene. How can the gene cloner give the bacteria an incentive for cloning extra DNA?
Fig. 4: Genes are cloned or copied by bacteria. (Image by D. Lee)
Fig. 5: DNA from any organism such as a soil bacteria (A) can be extracted (B) and the single gene of interest (dark line in B) in the DNA can be combined with a plasmid and cloned by E.coli bacteria (C). (Image by D. Lee)