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Study Guide Questions

1. Describe the use of a DNA probe and PCR for:
1. Rapid identification of an unknown bacterium.
2. Determining which of a group of bacterium are most closely related.

2. After contact with a patient's spinal fluid, a lab technician developed fever, nausea, and purple lesions on her neck and extremities. A throat culture grew gram-negative diplococci. What is the genus of the bacteria?

3. Define and describe, in reference to the lifecycle of the liver fluke Clonorchis sinensis, the intermediate host and definitive host. Also name the phylum and class that this animal belongs to.

4. Discuss the arguments for and against the classification of viruses as living organisms.

5. List the experimental requirements of Koch's postulates, and explain the exceptions to the requirements.

6. Given the limitations of Koch's postulates, what role do you see for molecular genetics and associated techniques in addressing the exceptions to the postulates?

7. Cancer patients undergoing chemotherapy are normally more susceptible to infections. However, a patient receiving an antitumor drug that inhibited cell division was resistant to Salmonella. Provide a possible mechanism for the resistance.

8. Describe the mode of action of each of the following antibiotics and explain what effect each one may have on host cells. Give an example of an organism that would be effectively treated for each drug.
1. Penicillin
2. Indinavir
3. Erythromycin
4. polymyxin B

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Describe the use of a DNA probe and PCR for:
Rapid identification of an unknown bacterium.

Since we are starting from an unknown bacterium, one can quickly isolate the DNA from a culture of the bacterium. Then use PCR method to quickly sequence various regions from the DNA and compare its DNA sequence profile to known profiles of bacteria for identification. In such a PCR method, one can use a degenerate primer for the PCR reaction or an array of specific primers. This is similar to the method forensic scientists use to identify potential criminals.
Alternatively, one can do some kind of Southern blot with an array of DNA probes to various different strains of bacteria. Whichever probe is able to hybridize or interact with the DNA sample, then that is the bacterium.

Determining which of a group of bacterium are most closely related.

Similar to the previous situations, one can use degenerate primers or an array of specific primers for various genes in the bacterial DNA in a PCR reaction to generate a genetic profile for each member of the group. Then, one can compare the genetic profiles to identify the ones that share the most genetic info.
Alternatively, one can do a genomic Southern with DNA probes against various crucial genes in the bacteria. The bacteria with the most similar hybridization patterns are likely to the most closely related ones.

After contact with a patient's spinal fluid, a lab technician developed fever, nausea, and purple lesions on her neck and extremities. A throat culture grew gram-negative diplococci. What is the genus of the bacteria?

Genus: Neisseria
http://en.wikipedia.org/wiki/Neisseria_meningitidis

Define and describe, in reference to the lifecycle of the liver fluke Clonorchis sinensis, the intermediate host and definitive host. Also name the phylum and class that this animal belongs to.

http://en.wikipedia.org/wiki/Clonorchis_sinensis
Phylum: Platyhelminthes
Class: Trematoda
The egg of a Clonorchis sinensis contains the miracidium that develops into the adult form and floats in freshwater until it is eaten by a snail. Once inside of the snail body (intermediate host), the miracidium hatches from the egg, and parasitically grows inside of the snail. The miracidium develops into a sporocyst, which in turn houses the asexual reproduction of redia, the next stage. The redia themselves house the asexual reproduction of free-swimming cercaria. This system of asexual reproduction allows for an exponential multiplication of cercaria individuals from one miracidium. This aids the Clonorchis in reproduction, because it enables the miracidium to captilatize on one chance occasion ...

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