Gene expression can be measured using cDNA microarrays. In this data set,
the gene expression of yeast cells was measured every 10 - 20 minutes over two
reproductive cycles of growth and budding. Gene expression was tracked by
using florescent probes on the cDNA microarrays. This creates a grid of spots.
The intensity of florescence in each spot is proportional to the quantity of
mRNA produced by the corresponding gene (ORF).
For the visualization, the expression intensity spots were mapped into a
Cartesian eigengene space using principal components. Each gene defines a
unique vector direction. The intensity of expression is the distance of a
glyph (arrow) on the vector from the origin. The color of the glyph shows the
gene function. The length of the trail behind each glyph is the rate of change
of gene expression. The angle between gene vectors shows correlation.
