You have grown cultures of the yeast Saccharomyces cerevisiae in a complex medium alone or supplemented with either glucose or ethanol. In the presence of glucose, available energy is abundant and the cells can therefore grow by fermenting glucose. In the presence of ethanol, however, the cells switch to a mostly aerobic respiration to meet their energy demands. They also shut down many of their anabolic pathways and activate catabolic pathways to produce more energy to better survive under these conditions. After the growth phase, you extract total mRNA from the cells, convert them to cDNA, and label them with a fluorescent molecule. You then hybridize the cDNAs to a yeast DNA microarray. Part of the results obtained by cluster analysis after fluorescent measurements is summarized in the following simplified diagram. Here, red and green indicate increase and decrease, respectively, in expression of a gene compared to that in the nonsupplemented medium. Which row (1 or 2) do you think corresponds to the glucose-supplemented medium?

Question

Quizplus · Accepted Answer

In glucose medium, compared to the nonsupplemented medium, the genes involved in ribosome biogenesis would be up-regulated (red) and those involved in the respiratory chain would be down-regulated (green). The opposite would occur in the presence of ethanol.

You Have Grown Cultures of the Yeast Saccharomyces Cerevisiae in a Complex