Pathology Question:
There are about 40 000 human genes and ESTs (expressed sequence tags) available on the Affymetrix Gene Chips for gene expression. Make some reasonable assumptions and estimate, for a normal organ, the number of genes that will appear to be expressed significantly greater than or less than the population norm (95% confidence interval).
Answer:
If we assume that each gene is independent and occurs in a normally distributed population, then one might expect approximately 5% of 40 000 or 2000 genes to appear over expressed or under expressed.