You Have Screened a Library by Nucleic Acid Hybridization with a Probe

Multiple Choice

You have screened a library by nucleic acid hybridization with a probe for a particular gene sequence. In the final phase of library screening, you apply an X-ray film to the membrane. The resulting autoradiogram has two black spots corresponding to two separate bacterial colonies. Which of the following explanations is the most likely?

A) The gene is large and fragmented between two different clones.
B) One of the spots must be an artifact because only one bacterial colony should contain the gene of interest.
C) The library screening was a failure because there should be blue and white colonies on the autoradiogram.
D) The temperature at which the high stringency washes was performed was too high.