This process, called genetic transformation, played a critical role in the history of molecular biology and the discovery that DNA was the genetic material. Today, transformation is not limited to bacteria, and in fact, is used routinely by molecular biologists to manipulate and study the behavior of genes. Transgenic plants expressing foreign genes have been constructed through transformation procedures. The lab described below demonstrates the properties of transformation using yeast and a simple colony color gene.
Yeast transformation involves several steps.
This experiment uses a yeast strain which is defective in an adenine synthesis gene, ADE1 . The metabolic defect in the mutants causes them to require adenine for growth and to accumulate a red pigment which causes the colonies to appear pink or red in color. When these ade1 mutant yeast are transformed with the normal ADE1 gene, they gain the ability to grow in the absence of adenine and form normal cream colored colonies. They behave in many ways like real chromosomes which carry genes in cells but plasmids are much more convenient. There are two types of plasmids carrying the yeast ADE1 gene available for use in this experiment.