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Exam 13: The Molecular Basis of Inheritance

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Question 31

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Use Figure 13.4 to answer the following question. Figure 13.4 -For a science fair project, two students decided to repeat the Hershey and Chase experiment, with modifications. They decided to label the nitrogen of the DNA, rather than the phosphate. They reasoned that each nucleotide has only one phosphate and two to five nitrogens. Thus, labeling the nitrogens would provide a stronger signal than labeling the phosphates. Why won't this experiment work?

A) There is no radioactive isotope of nitrogen.
B) Radioactive nitrogen has a half-life of 100,000 years, and the material would be too dangerous for too long.
C) Avery et al. have already concluded that this experiment showed inconclusive results.
D) Although there are more nitrogens in a nucleotide, labeled phosphates actually have 16 extra neutrons; therefore, they are more radioactive.
E) Amino acids (and thus proteins) also have nitrogen atoms; thus, the radioactivity would not distinguish between DNA and proteins.

F) A) and D)
G) B) and E)

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Question 32

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A biochemist isolates, purifies, and combines in a test tube a variety of molecules needed for DNA replication. When she adds some DNA to the mixture, replication occurs, but each DNA molecule consists of a normal strand paired with numerous segments of DNA a few hundred nucleotides long. What has she probably left out of the mixture?

A) DNA polymerase
B) DNA ligase
C) nucleotides
D) Okazaki fragments
E) primase

F) B) and C)
G) B) and E)

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Question 33

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In trying to determine whether DNA or protein is the genetic material, Hershey and Chase made use of which of the following facts?

Which of the following investigators was (were) responsible for the following discovery? In DNA from any species, the amount of adenine equals the amount of thymine, and the amount of guanine equals the amount of cytosine.

Which of the following sets of materials is required by both eukaryotes and prokaryotes for replication?

What is meant by the description "antiparallel" regarding the strands that make up DNA?

An Okazaki fragment has which of the following arrangements?

Figure 13.1 -A space probe returns with a culture of a microorganism found on a distant planet. Analysis shows that it is a carbon-based life-form that has DNA. You grow the cells in 15N medium for several generations and then transfer them to 14N medium. Which pattern in Figure 13.1 would you expect if the DNA was replicated in a conservative manner?

Use the list of choices below for the following questions: I. helicase II. DNA polymerase III III. ligase IV. DNA polymerase I V. primase -Which of the enzymes covalently connects segments of DNA?

In a nucleosome, the DNA is wrapped around

Use the following information to answer the next few questions. A eukaryotic gene has "sticky ends" produced by the restriction endonuclease EcoRI. The gene is added to a mixture containing EcoRI and a bacterial plasmid that carries two genes conferring resistance to ampicillin and tetracycline. The plasmid has one recognition site for EcoRI located in the tetracycline resistance gene. This mixture is incubated for several hours, exposed to DNA ligase, and then added to bacteria growing in nutrient broth. The bacteria are allowed to grow overnight and are streaked on a plate using a technique that produces isolated colonies that are clones of the original. Samples of these colonies are then grown in four different media: nutrient broth plus ampicillin, nutrient broth plus tetracycline, nutrient broth plus ampicillin and tetracycline, and nutrient broth without antibiotics. -Bacteria that do not take up any plasmids would grow on which media?

The leading and the lagging strands differ in that

Use the list of choices below for the following questions: I. helicase II. DNA polymerase III III. ligase IV. DNA polymerase I V. primase -Which of the enzymes separates the DNA strands during replication?

Figure 13.1 -Once the pattern found after one round of replication was observed, Meselson and Stahl could be confident of which of the following conclusions?

Use Figure 13.4 to answer the following question. Figure 13.4 -The segment of DNA shown in Figure 13.4 has restriction sites I and II, which create restriction fragments A, B, and C. Which of the gels produced by electrophoresis shown below best represents the separation and identity of these fragments?

In analyzing the number of different bases in a DNA sample, which result would be consistent with the base-pairing rules?

Which of the following modifications is least likely to alter the rate at which a DNA fragment moves through a gel during electrophoresis?

Given the damage caused by UV radiation, the kind of gene affected in those with XP is one whose product is involved with

E. coli cells grown on 15N medium are transferred to 14N medium and allowed to grow for two more generations (two rounds of DNA replication) . DNA extracted from these cells is centrifuged. What density distribution of DNA would you expect in this experiment?

Individuals with the disorder xeroderma pigmentosum are hypersensitive to sunlight. This occurs because their cells are impaired in what way?