4. The DNA structure proposed by Watson and Crick suggested a replication model

Question

4. The DNA structure proposed by Watson and Crick suggested a replication model which was tested by Meselson and Stahl. They used nitrogen isotopes to label replicating DNA which was then separated into bands on a density gradient. The three possible models of replication predicted different numbers of bands after one and then two DNA replications. For the conservative model of DNA replication two bands were expected after the first round of replication. The semiconservative model predicted the presence of _______ band(s) after the second replication. a. 2 b. 4 c. 3 d. 1 e. 8
5. A common polymorphism affecting the P450 enzyme CYP2D6 causes defective oxidation of many different drugs which require oxidative metabolism for efficacy. For example the antihypertensive drug debrisoquine is not oxidized to 4 hydroxy-debrisoquine in some patients and the mutant P450 enzyme is a
suspected cause. In a large clinical trial 600 couples, who were themselves capable of metabolizing debrisoquine had at least one child incapable of oxidizing the drug. There were 987 total children; 750 of them were able to metabolize debrisoquine. ______ children were not able to metabolize the drug.
a. 400 b. 237 c. 207 d. 314 e. 1054
6. If the P450 mutant acts in a recessive manner and this defect is a single gene disorder, we may calculate the expected numbers of normal and oxidatively deficient children as _____ normal and _________ deficient.
a. 635.25 211.75 b. 840 7 c. 200 647
d. 740.25 246.75 e. 84.7 762.3
7. In doing a Chi-square analysis of the data from these children I will use ____ as the number of degrees of freedom.
a. 3 b. 2 c. 1 d. 0 e. 9.76

Explanation / Answer

4. d 5.. b 6. c 7. b

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