The Molecular Basis of Inheritance

Who conducted the X-ray diffraction studies that were key to the discovery of the structure of DNA? Griffith Franklin Meselson and Stahl Chargaff McClintock Answer: B

Who conducted the X-ray diffraction studies that were key to the discovery of the structure of DNA? Griffith Franklin Meselson and Stahl Chargaff McClintock 3

How do the leading and the lagging strands differ? The leading strand is synthesized in the same direction as the movement of the replication fork, whereas the lagging strand is synthesized in the opposite direction. The leading strand is synthesized at twice the rate of the lagging strand. The lagging strand is synthesized continuously, whereas the leading strand is synthesized in short fragments that are ultimately stitched together. The leading strand is synthesized by adding nucleotides to the 3' end of the growing strand, whereas the lagging strand is synthesized by adding nucleotides to the 5' end. Answer: A DNA is made only in the 5' to 3' direction. 4

How do the leading and the lagging strands differ? The leading strand is synthesized in the same direction as the movement of the replication fork, whereas the lagging strand is synthesized in the opposite direction. The leading strand is synthesized at twice the rate of the lagging strand. The lagging strand is synthesized continuously, whereas the leading strand is synthesized in short fragments that are ultimately stitched together. The leading strand is synthesized by adding nucleotides to the 3' end of the growing strand, whereas the lagging strand is synthesized by adding nucleotides to the 5' end. 5

What kind of evidence about the structure of DNA came from each of the following branches of science? physics chemistry biology Answer: X-ray crystallography, B. The nature of ribose sugar, purines, and pyrimidines, C. Data from Chargaff on the ratios between A and T and so on, 6

What kind of evidence about the structure of DNA came from each of the following branches of science? physics: X-ray crystallography chemistry: The nature of ribose sugar, purines, and pyrimidines biology: Data from Chargaff on the ratios between A and T and so on Answer: X-ray crystallography, B. The nature of ribose sugar, purines, and pyrimidines, C. Data from Chargaff on the ratios between A and T and so on, 7

If the result of the Hershey and Chase experiment had been that radioactive sulfur (35S) was found inside the cells instead of radioactive phosphorus (32P), what could have been concluded? Answer: It would have been concluded that protein functions as the genetic material (this, of course, did not occur). Figure 13.4. 8

If the result of the Hershey and Chase experiment had been that radioactive sulfur (35S) was found inside the cells instead of radioactive phosphorus (32P), what could have been concluded? It would have been concluded that protein functions as the genetic material (this, of course, did not occur). Answer: It would have been concluded that protein functions as the genetic material (this, of course, did not occur). Figure 13.4. 9

Define and diagram “semiconservative” as it applies to DNA replication. Answer: A newly replicated DNA has one strand that had been present in the original and one completely new strand. Concept 13.2. 10

Telomeres, or the ends of linear chromosomes, have special structure and function, even though they are noncoding. Describe their structure and function. Answer: Figure 13.20, Concept 13.2. Telomeres may have a major impact on students’ lives, as they may hold the secret to longer life. 11

What enzyme does a gamete-producing cell include that compensates for replication-associated shortening? DNA polymerase II ligase telomerase DNA nuclease proofreading enzyme Answer: C 12

What enzyme does a gamete-producing cell include that compensates for replication-associated shortening? DNA polymerase II ligase telomerase DNA nuclease proofreading enzyme 13

Which of the following is true of heterochromatin but not of euchromatin? It is accessible to enzymes needed for gene expression. It becomes less tightly compacted after cell division. It includes DNA primarily found in expressed genes. It appears more pale when observed microscopically. It remains tightly coiled at the G1 phase. Answer: E 14

Which of the following is true of heterochromatin but not of euchromatin? It is accessible to enzymes needed for gene expression. It becomes less tightly compacted after cell division. It includes DNA primarily found in expressed genes. It appears more pale when observed microscopically. It remains tightly coiled at the G1 phase. 15

Which of the following results from Griffith’s experiment is an example of transformation? Mouse dies after being injected with living S cells. Mouse is healthy after being injected with living R cells. Mouse is healthy after being injected with heat-killed S cells. Mouse dies after being injected with a mixture of heat-killed S and living R cells. In blood samples from the mouse in D, living S cells were found. Answer: D

Which of the following results from Griffith’s experiment is an example of transformation? Mouse dies after being injected with living S cells. Mouse is healthy after being injected with living R cells. Mouse is healthy after being injected with heat-killed S cells. Mouse dies after being injected with a mixture of heat-killed S and living R cells. In blood samples from the mouse in D, living S cells were found.

Nitrogenous bases are paired in specific combinations Nitrogenous bases are paired in specific combinations. Which of the following does not provide evidence to support this conclusion? A purine-purine pair is too wide to account for the 2-nm diameter of the double helix. A pyrimidine-pyrimidine pair is too narrow to account for the 2-nm diameter of the double helix. The X-ray data suggested that the double helix had a uniform diameter. Whenever one strand of DNA has an A, the partner strand has a T. The pairs of nitrogenous bases are held together by hydrogen bonds. Answer: E

Nitrogenous bases are paired in specific combinations Nitrogenous bases are paired in specific combinations. Which of the following does not provide evidence to support this conclusion? A purine-purine pair is too wide to account for the 2-nm diameter of the double helix. A pyrimidine-pyrimidine pair is too narrow to account for the 2-nm diameter of the double helix. The X-ray data suggested that the double helix had a uniform diameter. Whenever one strand of DNA has an A, the partner strand has a T. The pairs of nitrogenous bases are held together by hydrogen bonds.

Scientific Skills Exercise Tables like the one shown here are useful for organizing sets of data representing a common set of values (in this case, percentages of A, G, C, and T) for a number of different samples (in this case, species).

Does the distribution of bases in sea urchin DNA and salmon DNA follow Chargaff’s rules? Yes, because the %A + %T is greater than the %G + %C in both species. No, because %A + %T does not equal %G + %C in both species. Yes, because the %A approximately equals the %T and the %G approximately equals the %C in both species. No, because %A is higher than %T and %G is higher than %C in both species. Answer: C

Does the distribution of bases in sea urchin DNA and salmon DNA follow Chargaff’s rules? Yes, because the %A + %T is greater than the %G + %C in both species. No, because %A + %T does not equal %G + %C in both species. Yes, because the %A approximately equals the %T and the %G approximately equals the %C in both species. No, because %A is higher than %T and %G is higher than %C in both species. Answer: C

What is the %T in wheat DNA? approximately 22% approximately 23% approximately 28% approximately 45% Answer: C

What is the %T in wheat DNA? approximately 22% approximately 23% approximately 28% approximately 45%