After meiosis for a crayfish with 200 chromosomes in its somatic cells, _____ sperm are produced with _____ chromosomes in each sperm.
A. 2; 200
B. 4; 100
C. 2; 100
D. 4; 200
Answer: B. 4; 100
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How might absorption of organic compounds into clays assist in their aggregation and organization
into membrane-bound protocells?
a. Clays contain many minerals in extremely thin layers and readily repel ions, forcing multiple chemical interactions. b. Clays are highly structured, contain water, and store potential energy that could drive the chemical reactions forward. c. Clays lack water, forcing the concentration of the organic molecules and thus driving multiple interactions. d. Clays are extremely resistant to temperature changes and thus would insulate the organic compounds from temperature changes in the atmosphere. e. None of the above statements accurately explain clays’ possible roles in the formation of protocells.
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 of the following rows is a correct match?
A. Row 1
B. Row 2
C. Row 3
D. Row 4
Which of the following might cause an exponential increase in deer populations across the United States?
A) increase in atmospheric carbon dioxide levels B) reduction in the population of wolves and bobcats C) reduction in parasites that are found in emaciated deer D) improvement in forest soil