1. Microarrays (Gene Chips) Pioneered by Pat Brown in mid 1990’s To monitor thousands of mRNAs simultaneously Comparative Northern blot on thousands of genes

2. Two mRNA samples a ‘reference’ and a ‘experimental’

3. Two mRNA samples a ‘reference’ and a ‘experimental’ For example, yeast cells growing via anaerobic metabolism vs. yeast cells growing via aerobic metabolism

4. Purify mRNAs from each sample Bind to –TTTTTTTTTT–beads note that you get a population of mRNAs Reverse Transcribe to get a population of cDNAs

5. “Label” the two mRNA samples differently Reference sample is covalently attached to the fluor Cy3 glows green under UV light

6. “Label” the two mRNA samples differently Reference sample is covalently attached to the fluor Cy3 glows green under UV light Experimental sample is covalently attached to the fluor Cy5 glows red under UV light

7. Prepare the Microarray PCR product corresponding to every yeast gene (~6200) Attach to a glass slide at a known location Entire array is 18mm by 18mm (postage stamp)

8. Prepare the Microarray PCR product corresponding to every yeast gene (~6200) Attach to a glass slide at a known location Entire array is 18mm by 18mm (postage stamp) PFK1 NCC1

9. Mix reference and experimental cDNAs Add to microarray Using a microscope and a computer, Quantitate ‘greeness’ and ‘redness’ of each spot

10. DeRisi et al., Science 278: 685 1997

11. Consider the NCC Gene if NCC mRNA is equally abundant in reference and experimental population: NCC sequence Spot on Microarray

12. Consider the NCC Gene if NCC mRNA is equally abundant in reference and experimental population: Spot on Microarray Equal green and red = Yellow

13. Consider the NCC Gene if NCC mRNA is more abundant in reference than experimental population (repressed by aerobic growth): Spot on Microarray Spot glows green

14. Consider the NCC Gene if NCC mRNA is less abundant in reference than experimental population (induced by aerobic growth): Spot on Microarray Spot glows red

15. Microarrays: Compare amounts of several thousand mRNAs Red, Green, Yellow or Black Between two conditions, experimental and reference looking for induction or repression

16. Following the timecourse: These seven genes all encode proteins in the electron transport chain.

17. Following the timecourse: These seven genes all encode proteins in the electron transport chain. These seven genes all contain the same enhancer sequence: CCAAT Binds the transcription factor Hap2/3/4p