In Yeast,expression of the GAL Genes is Induced When There

Question

In yeast,expression of the GAL genes is induced when there is ________ in the culture medium.
A)glucose
B)lactose
C)galactose
D)maltose
E)Any of these

Accepted Answer

GAL genes are induced by the presence of galactose in the culture medium. The GAL system in yeast is a galactose-inducible gene expression system. In the presence of galactose, it activates the GAL switch, which activates the expression of genes involved in galactose metabolism. The GAL switch is repressed in the presence of glucose, and also by high levels of fructose and mannose. Therefore, expression of GAL genes is induced specifically by galactose.