10 May 1985
Vol 228, Issue 4700

About The Cover

Autoregulation of yeast copperthionein gene. Yeast cells were grown on a bromthymol blue galactose indicator plate on which positive cells are yellow and negative cells are white. Both strains contain an episomal fusion gene in which yeast copperthionein regulatory sequences drive the expression of bacterial galactokinase. The cells to the left contain multiple copies of the chromosomal structural gene for copperthionein and are galactose-negative. The cells to the right lack an intact copperthionein gene and are galactose-positive due to increased basal transcription of the fusion gene. See page 685. [Dean H. Hamer, National Institutes of Health, Bethesda, Maryland 20205]