The oil globules that result when a water and oil
mixture is shaken are due to a(n) __________
interaction.
a. acidic
b. basic
c. hydrophilic
d. hydrophobic
e. ionic
Answer: d
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How would you best explain the existence of a mountain range that has abundant conifer trees, ferns, and mosses on the east side, but only sparse shrubby plants on the west side?
A. Adiabatic cooling leads to temperature gradients that produce the differing plant communities. B. Differences in solar intensity produce the differing plant communities. C. Precipitation differences due to a rain shadow on the west side produce the differing plant communities. D. Differences in the specific heat of the two sides of the mountain produce the differing plant communities.
Assume that a culture of E. coli was grown for approximately 50 generations in 15N (provided in the medium in the ammonium ion), which is a heavy isotope of nitrogen (14N). You extract the DNA from the culture, and it has a density of 1
723 gm/cm3 (water = 1.00 gm/cm3). From the literature, you determine that DNA containing only the common form of nitrogen, 14N, has a density of 1.700 gm/cm3. Bacteria from the 15N culture were washed in buffer and transferred to 14N medium for one generation immediately after which the DNA was extracted and its density determined. (a) What would be the expected density of the extracted DNA? (b) After you heat the extracted DNA until it completely denatures (95°C for 15 minutes), what would you expect the density of the DNA in the denatured extract to be? For the purposes of this question, assume that DNA has the same density regardless of whether it is single- or double-stranded. (c) Assuming that the molar percentage of adenine in the extracted DNA was 20 percent, what would be the expected molar percentages of the other nitrogenous bases in this DNA? (d) Assume that a fraction of the extracted DNA was digested to completion with the enzyme snake venom diesterase. This enzyme cleaves between the phosphate and the 3' carbon. Present a "simplified" diagram that would illustrate the structure of the predominant resulting molecule.
Which statement about forensic DNA profiling is false?
A) The results are always given in terms of the probability that two individuals' DNA could give the exact same genetic profile. B) The technique takes advantage of the fact that portions of the human genome vary greatly throughout the population. C) Because the tests are often run on very small biological samples, such as drops of blood, PCR reactions are used to amplify the DNA before the profiling begins. D) After a profile has been done, a complete DNA sequence is often used to verify the results. E) The strength of DNA fingerprinting is that it determines the alleles that an individual carries at not 1 but 13 different STR locations
A cystic fibrosis patient develops a severe respiratory infection that resists treatment with standard antibiotics. A specimen from the lungs is greenish in color and contains aerobic motile Gram-negative bacilli. The bacteria are oxidase positive. The patient is probably infected with
A. Bordetella pertussis. B. Burkholderia cepacia. C. Klebsiella pneumoniae. D. Pseudomonas aeruginosa. E. Serratia marcescens.