Solutions to 100 passage-based Biology questions

Roundworm infections are fought by the bodys immune

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Unformatted text preview: incidences of roundworm infections. Roundworm infections are fought by the body’s immune system. When this natural target of the immune system is removed, as in more developed countries, the immune system is bored and begins to find other, inappropriate targets. 25. C. CD is not treatable by surgery because it is systemic to the entire GI tract (while UC is usually confined to the colon and removing a diseased section of colon is a surgical option). 26. B. The only clear result from Experiment 1 is that following irradiation, no cultures were able to grow on medium with ampicillin. This observation should not eliminate the possibility that other mutations may have occurred in the tube. The medium used in the dish was only designed to test for ampicillin-resistance among the normally sensitive cells. 27. B. The passage reveals that single cells can grow into colonies after incubation. Therefore, the two colonies that grew in Experiment 2 were derived from at least one cell each. The Page 3 of 12 observation that they grew on a medium with ampicillin indicates that they cells became ampicillin-resistant after the second irradiation. 28. C. Medium Y contains lactose instead of glucose. Cells from Colony B were unable to grow on this lactose medium. Both colonies were able to grown on a minimal medium (Medium X, containing glucose) as well as on ampicillin. 29. A. The passage states that normal cells can grow on a lactose medium because they have the enzymes needed to convert it to glucose. If cells from Colony B can no longer grow on lactose, the irradiation may have affected the gene coding for this enzymes (or one of the enzymes) Lactose is still nutritious for Colony A, and the lactose medium was not irradiated – only the test-tube suspension was irradiated. Finally, the colonies were placed on separate dishes – no competition was involved. 30. C. As stated earlier (question 25), we cannot eliminate the possibility that the mutation at the lactose enzyme locus could have occurred in Experiment 1. Experiment 1 was sim...
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This note was uploaded on 03/23/2011 for the course CHEM 100 taught by Professor Vallis during the Spring '11 term at Dalhousie.

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