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Chapter 28: Q 23E (page 963)
Question: The DNA of sea urchins contains about 32% A. What percentages of the other three bases would you expect in sea urchin DNA? Explain.
The percentages of bases in the DNA of sea urchins are:
| Base percentage | |||
|---|---|---|---|
| Adenine | Guanine | Thymine | Cytosine |
| 32% | 18% | 32% | 18% |
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Melamine, used as a fire retardant and a component of the writing surface of white boards, can be prepared from s-trichlorotriazine through a series of SNAr reactions with ammonia. The first substitution takes place rapidly at room temperature. The second substitution takes place near 100 掳C, and the third substitution requires even higher temperature and pressure. Provide an explanation for this reactivity.
Question: The codon UAA stops protein synthesis. Why does the sequence UAA in the following stretch of mRNA not cause any problems?
-GCA-UUC-GAG-GUA-ACG-CCC-
Propose structures for alcohols that have the following NMR spectra:
Propose a mechanism to account for the cleavage of the 尾-cyanoethyl protecting group from the phosphate groups on treatment with aqueous ammonia. (Acrylonitrile, H鈧侰=CHCN, is a by-product.) What kind of reaction is occurring?
Write molecular formulas for compounds that show the following molecular ions in their high-resolution mass spectra, assuming that C, H, N, and O might be present. The exact atomic masses are: 1.00783\(\left( {{}^1{\bf{H}}} \right)\), 12.00000\(\left( {{}^{12}C} \right)\), 14.00307\(\left( {{}^{14}N} \right)\), 15.99491\(\left( {{}^{16}O} \right)\).
(a)\({{\bf{M}}^ + }{\rm{ = 98}}{\rm{.0844}}\)
(b\({{\bf{M}}^ + }{\rm{ = 123}}{\rm{.0320}}\)
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