Question:

A first-year medical student is new to the lab and wants to know if a well-studied gene is transcribed in the sample of cytoplasmic extracts she is given. Which of the following techniques should she use to quickly find out?

Correct Answer: B.  Northern blot

Northern blot employs a hybridization probe (of the gene of interest) to identify complementary RNA sequences. Southern blot is used for hybridization to DNA sequences (which would not tell you anything about expression). Western blot is used for protein identification (not gene expression). Southwestern blot is used to determine proteins that bind to DNA. Column chromatography is used to fractionate extracts based on a number of factors (size, charge, pH, etc.), but won’t identify individual genes.