To study the function of the essential cytosolic Hsc70 genes in yeast,researchers constructed a shuttle vector in which a copy of the Hsc70 gene was ligated to the GAL1 promoter.The vector was then introduced into haploid yeast cells in which all four copies of the Hsc70 genes had been disrupted.Following introduction of the vector,you would expect that
A)the yeast cells would grow on both glucose and galactose media.
B)the yeast cells would grow on glucose but not galactose medium.
C)the yeast cells would grow on galactose but not glucose medium.
D)on transfer to either glucose or galactose medium,the vector-carrying cells would eventually stop growing because of insufficient Hsc70 activity.

Question

Quizplus · Accepted Answer

The GAL1 promoter is inducible by galactose, meaning that the Hsc70 gene will only be expressed in the presence of galactose. Since all four copies of the essential Hsc70 genes have been disrupted in the haploid yeast cells, the only source of Hsc70 expression will be from the Hsc70 gene ligated to the GAL1 promoter in the shuttle vector. Therefore, the yeast cells carrying the vector will only be able to grow on galactose medium, where they can induce Hsc70 expression. On glucose medium, where the GAL1 promoter is not induced, the yeast cells will not be able to grow due to the lack of Hsc70 activity.

To Study the Function of the Essential Cytosolic Hsc70 Genes