Vibrio cholerae is a bacteria that causes cholera, characterized by severe dehydration and watery diarrhea. During a cholera outbreak, polymerase chain reaction (PCR) was used to detect the presence of V. cholerae in oysters from different areas by extracting DNA from homogenized oyster samples, amplifying DNA using a primer for the V. cholerae hemolysin gene, and running the samples on a gel after PCR and enzyme digestion.

1. Vibrio cholerae is a pathogenic bacteria that can cause a disease known as Cholera. Signs and
symptoms of Cholera indude severe dehydration, profuse watery diarrhea, (described as "rice-
water stools"), and vomiting. The organism is transmitted in drinking. water and/or food. During
a recent outbreak of Cholera PCR was used to detect the presence of Viorio choverae in oysters.
Oysters from different areas were homogenized (cell membranes lysed), then the DNA was
extracted from the homogenates. The DNA amplifled by PCR then digested by the restriction
enzyme HinclI. A primer for the hemolysin gene or V , cholerae was used for the PCR reaction.
After PCR, the samples were ran on a gel. A picture of the gel is below. Based on the
information above and the picture of the gel answer the following questions: 1. Which, if any, of
the oyster samples are positive for V . choleras? Explain how you know. 2. Briefly explain one
advantage of using PCR to identify if a bacterial organsm is in a biological sample.