Essential Genetics 6th Edition by Daniel Hartl

Exercise 19

A functional genomics experiment is carried out in E.coli to examine global levels of gene expression in various types of minimal growth medium. RNA extracted from the experimental culture is labeled with a molecule that fluoresces red, and RNA extracted from the control culture is labeled with a molecule that fluoresces green. The experimental and control samples are mixed prior to hybridization. Shown here are spots on the microarray corresponding to five genes: trpE (the first gene in the tryptophan biosynthetic operon), lacI , lacZ , lacY , and crp (which encodes the cyclic AMP receptor protein). Color the spots red, green, or yellow according to the relative levels of expression of each gene in the experimental and control cultures. ( Hint : Before answering, think carefully about how the cyclic AMP receptor protein co-regulates the lac operon.)