The transcription response to YPD medium of spores pre-incubated in different components of the medium. (a) The experimental design. Mature spores (prepared from strain DS1) were incubated in either component of the medium (glucose or 'nitrogen') for two hours and were then transferred to rich medium (YPD) to allow spore germination. Each circle represents a time point at which genome-wide gene expression was monitored; RNA was extracted, labeled and hybridized to micorarray complementary to all (approximately 6,200) yeast ORFs. The reference RNA was a mixture of RNA from Mata and Matα log phase cells. (b) The matrix of pairwise correlations (see legend for Figure 4) describing the similarity in gene expression during spore germination (in YPD medium) of spores pre-incubated in glucose or 'nitrogen'. Correlations with normal germination (without pre-incubation, see Figure 2a) are also presented here. *Correlations are color-coded according to the bar shown. (c) Enlargements of the parts marked in circles in the correlation matrix presented in (b).