Quiz 1. Bloe8 Chapter question online student quizzes

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1 Bloe8 Chapter question online student quizzes Questions are organized by section number and have an (F), (C), or (A) at the beginning to designate the modified Bloom categories used in the test item files. Quiz 1 (F)1. Identify the research that first provided the basis for the following statement: DNA is the genetic material. a. Watson and Crick proposed a new model for DNA structure. b. Avery, MacLeod, and McCarty isolated the material that transformed R-strain bacteria into S-strain bacteria. c. Chargaff found that DNA contains equal amounts of adenine and thymine, as well as equal amounts of cytosine and guanine. d. Wilkins and Franklin used X-ray diffraction to study DNA structure. Hint: These experiments had to prove that molecules identified as DNA could carry information from one place to another. You can review this in sections 9.1 in your textbook. a. Incorrect. Watson and Crick were able to synthesize all the available data into a model for the structure of DNA. b. Correct. Avery, MacLeod, and McCarty were able to purify the DNA molecules from the S-strain bacteria that could transform the R-strain. c. Incorrect. Chargaff's findings were important in determining the structure of DNA. d. Incorrect. Wilkins and Franklin's findings were important in determining the structure of DNA. (C)2. An interpretation of Griffith's experiments is that: a. fragments of DNA containing genes were taken up by the R-strain bacteria. b. genetic material must have been transferred from the R-strain bacteria into the S-strain bacteria. c. the genetic material must be protein. d. base-pairing accounts for the amounts of each base found. Hint: Griffith successfully transformed harmless bacteria into lethal bacteria. You can review this in sections 9.1 in your textbook. a. Correct. The genes contained in these DNA fragments transformed the harmless R-strain bacteria into deadly S-strain bacteria. b. Incorrect. Griffith's results indicated something entirely different. c. Incorrect. This is not true. Griffith's results provided a means of identifying the genetic material, without providing the answer itself. d. Incorrect. Griffith's findings did not investigate the structure of DNA. (C)3. DNA structure can be described as a twisted ladder. Imagine you are climbing a model of DNA, just as if you were climbing a ladder. What parts of a nucleotide are your feet touching as you climb?

2 a. the sugars b. the nitrogenous bases c. the phosphates Hint: This is analogous to the rungs of the ladder. Please review section 9.2 of the text. a. Incorrect. The sugars are parts of the uprights. b. Correct. The bases form the "rungs" of the ladder. c. Incorrect. The phosphates are parts of the uprights. (C)4. Human chromosomes range in size dramatically, with the smallest (sex chromosome Y) being many times smaller than the largest (autosomal chromosome 1). What is responsible for determining the size of a chromosome? a. the length of the DNA molecule in it b. the amount of protein associated with it c. the number of DNA molecules in it Hint: Think about what would make a chromosome larger. See section 9.2 of your textbook. a. Correct. The length of a chromosome is directly related to the length of the DNA molecule in it. b. Incorrect. Proteins help provide chromosome structure but do not determine a chromosome s size. c. Incorrect. All chromosomes contain one DNA molecule. (C)5. Imagine that you are studying a newly discovered bacterium from a hot springs in Yellowstone National Park. When you examine the nucleotide composition of this organism, you find that 10% of the nucleotides in its DNA are adenine. What percentage of nucleotides are guanine? Explain. a. 10%, because A pairs with G b. 90%, because 100% minus 10% equals 90% c. 40%, because A pairs with T (accounting for 20% of the bases), leaving 80% of the nucleotides as G-C base pairs; half of 80% is 40%. Hint: Think about the base-pairing relationships in DNA. Please review section 9.2 of your text. a. Incorrect. Adenine pairs with thymine. b. Incorrect. You know that adenine pairs with thymine; if there is 10% adenine, there must also be 10% thymine. So the maximum amount of other nucleotides is 80%. c. Correct. Because of DNA's double-helix structure and base-pairing rules, if you know the percentage of one nucleotide in a DNA sample, you can figure out the percentage of all of the others. (C)6. Which one of the following statements is true of the sugar-phosphate backbone of DNA? a. The two sugar-phosphate strands are oriented in the same direction. b. The two sugar-phosphate strands are oriented in the opposite direction. c. The two sugar-phosphate strands can be oriented in either the same or the opposite direction. d. The sugar-phosphate backbone is in the center of the DNA molecule. Hint: The orientation of the sugar-phosphate backbones is an important part of DNA structure. This is

3 explained in section 9.2 of your textbook. a. Incorrect. There is a different relationship between the two strands. b. Correct. The phosphate end of one strand is next to the sugar end of the opposite strand. c. Incorrect. The two strands have a specific orientation relative to each other. d. Incorrect. The sugar-phosphate backbone is on the outside of the molecule. (F)7. In a DNA helix, all of the following are true EXCEPT: a. the nitrogenous bases are covalently bonded to each other. b. the nitrogenous bases are in the inner part of the helix. c. the strands are in opposite orientation. d. cytosine pairs with guanine. Hint: This question deals with properties of the DNA helix. You can review this in section 9.2 in your textbook. a. Correct. The nitrogen-containing bases are hydrogen-bonded to each other. b. Incorrect. The bases are found in the inside of the helix. c. Incorrect. The opposing orientation of the two strands is an important feature of the DNA helix. d. Incorrect. Cytosines do pair with guanines. (C)8. Information in DNA is carried in. a. the sugar-phosphate backbone of one DNA strand b. the base pairs between nucleotides in the two DNA strands c. the proteins that bind to the DNA double helix d. the order of the nucleotide bases in one DNA strand Answer: d Hint: This is one of the important capabilities of nucleic acids. Please review section 9.3 of your text. a. Incorrect. The sugar-phosphate backbone is a simple, repeating structure; it contains no information. b. Incorrect. The base-pairs are sets of hydrogen bonds that hold the two strands of the double helix together: A on one strand pairs with T on the other; C on one strand pairs with G on the other. This pairing does not carry genetic information. c. Incorrect. Proteins are key regulators of which genes get transcribed and which do not, but they don t carry genetic information. d. Correct. The order of nucleotides in a gene corresponds to the order of amino acids in the protein it encodes. Note that each gene has two DNA strands, but only one strand is transcribed. (The nontranscribed strand is needed when DNA is replicated.) (C)9. Multiple replication bubbles on a single eukaryotic chromosome: a. allow for rapid replication of eukaryotic DNA. b. do not occur. c. lead to many DNA strands being synthesized from the same chromosome simultaneously. d. occur to ensure that the DNA is replicated faithfully.

4 Hint: Eukaryotic chromosomes can be very large. See section 9.4 in your textbook. a. Correct. Since eukaryotic chromosomes are so large, replication must take place at multiple sites on the chromosome to speed the process. b. Incorrect. Multiple replications bubbles are common during replication. c. Incorrect. The replication bubbles are designed to replicate the chromosome to make two duplicated chromosomes. d. Incorrect. There are a number of other mechanisms in place to ensure the integrity of DNA replication. (F)10. DNA polymerase: a. can replicate both strands of DNA in a continuous manner. b. can add nucleotides only to the free sugar end of a DNA molecule. c. can bond short stretches of DNA together. d. molecules in a replication bubble move toward each other. Hint: DNA polymerase is the enzyme that synthesizes the DNA strand. DNA replication is discussed in section 9.4 in your textbook. a. Incorrect. The opposite orientation of the two DNA strands in a double helix prevents this from occurring. b. Correct. This is part of the specificity of the enzyme. c. Incorrect. This process requires DNA ligase. See d. Incorrect. Within a replication bubble, the two forks move in opposite directions away from each other (F)11. DNA ligase has all of the functions listed below EXCEPT: a. repair of damaged DNA. b. piecing together of small pieces of DNA during replication. c. covalently bonding DNA strands made by adjoining replication forks. d. covalently bonding small DNA pieces together during the synthesis of both strands of a double helix. Answer: d Hint: DNA ligase plays an important role during the replication of DNA. DNA replication is discussed in section 9.4 in your textbook. a. Incorrect. This is one of the functions of DNA ligase. b. Incorrect. This is one of the functions of DNA ligase. c. Incorrect. This is a function of DNA ligase. d. Correct. DNA ligase is responsible for bonding together DNA pieces during the synthesis of one strand, but not both. (F)12. Which of the following statements is FALSE? a. DNA replication involves uncoiling of the parental DNA molecule. b. DNA replication produces a long, continuous strand and a series of short pieces. c. DNA ligase is required in the synthesis of one strand. d. Both parental strands end up in the same daughter strand after replication. e. DNA polymerase molecules move toward the replication fork on both strands.

5 Answer: d Hint: DNA synthesis occurs by a well-defined process. DNA replication is discussed in section 9.4 in your textbook. a. Incorrect. This is a true statement. b. Incorrect. This statement is true. c. Incorrect. Since one strand must be synthesized in short pieces, DNA ligase is needed to bond these pieces together. d. Correct. Each daughter strand receives one of the original parental strands. e. Incorrect. The two polymerases move in opposite directions. (C)13. The purpose of DNA replication is to produce: a. two similar DNA double helices differing in a small number of specific sites. b. two very different DNA double helices. c. two identical DNA double helices. d. one copy which is identical to the parental DNA molecule and one which is totally different. e. a single-stranded DNA molecule from the double-stranded parent DNA. Hint: DNA replication happens in cells that will divide. DNA replication is covered in section 9.4. a. Incorrect. There is no mechanism in place to generate specific differences in the DNA molecules. b. Incorrect. The process is not designed to generate different molecules. c. Correct. DNA replication is designed to accurately copy the original DNA double helix into two exact copies. d. Incorrect. DNA replication replicates the DNA. e. Incorrect. The end result will be two double helices. (F)14. Which of the following can cause errors to accumulate in DNA? a. high levels of metabolic activity b. ultraviolet light c. cold temperatures d. None of the above is correct. Hint: Are suntans/burns healthy? See section 9.5 in your textbook. a. Incorrect. Metabolic activity is not one of the sources of error. b. Correct. Ultraviolet can cause mutations in DNA. c. Incorrect. Cold is not one of the sources of error. d. Incorrect. One of the other choices can cause errors to accumulate in DNA. (F)15. What is the approximate error rate for DNA polymerase? a. one error for every 100 bases added b. one error for every 10,000 bases added c. one error for every billion bases added Hint: The error rate of DNA polymerases is higher than that of replication.. See section 9.5 in your textbook.

6 a. Incorrect. The error rate is much better than this. b. Correct. DNA polymerases make a mistake about once in every 10,000 bases. c. Incorrect. Although this is the overall error rate of replication, DNA polymerase is not by itself this accurate. Quiz 2 (C)1. Before it was actually determined, many scientists had trouble believing that DNA was the genetic material. This is most likely because: a. it was known that proteins could be passed from generation to generation. b. the number of nucleotides in DNA is very small. c. destruction of proteins prevented genetic transformation. d. it was known that RNA could be passed from generation to generation. Hint: How many different types of nucteotides are in DNA? You can review this in sections 9.1 in your textbook. a. Incorrect. This information is not true. b. Correct. Some scientists believed proteins, with their 20 amino acids, were a better choice. c. Incorrect. Destruction of the DNA component prevented genetic transformation of bacteria. d. Incorrect. This information is not true. (C)2. How can a cell, killed by heat in order to render it harmless, somehow still act to transform a second strain of bacterium from a noninfectious form into a disease carrier (i.e., a pathogen)? a. The second (noninfectious) strain of bacterium was changed into a disease carrier (i.e., pathogen) by something from the heat-killed cell. b. The heat-killed cell wasn't really dead. c. The second (noninfectious) strain spontaneously mutated into a deadly pathogen. d. Both the second and third answers above are correct. Hint: Carefully consider exactly what dead means. Death assumes that there is an interruption in biochemical processes necessary for cell survival, rather than total destruction of the cell. See section 9.1 of the textbook. a. Correct. Even though cells of the heat-killed strain were dead, not everything was destroyed by the heat. Later, it was found that this substance was DNA. b. Incorrect. The heat-killed cells are dead. c. Incorrect. While mutations can and do occur, transformation of one strain into a carbon copy of another bacterial strain is exceedingly unlikely. d. Incorrect. Neither answers is correct. (C)3. The structure of DNA explained Chargaff's observations because: a. the DNA molecule is a regular, repeating molecule. b. the twisting of the DNA required certain amounts of bases. c. adenines were found to pair with thymines and cytosines with guanines. d. the sequence of bases is crucial to the storage of information. e. there are only four different bases.

7 Hint: One of Chargaff s observations was that the amounts of cytosine and guanine were always equal in DNA. This is explained in Section 9.2 in your textbook. a. Incorrect. Research by Wilkins and Franklin indicated that this was the case. See section 9.2 in your textbook. b. Incorrect. Although the twisting of DNA is dependent upon the formation of the double helix, this does not explain Chargaff's findings. c. Correct. Chargaff found DNA contained equal amounts of adenine and thymine, as well as equal amounts of cytosine and guanine. d. Incorrect. This does not explain Chargaff's findings. e. Incorrect. This piece of information also does not explain Chargaff's findings. (C)4. The two strands of DNA which make up a double helix: a. are identical to each other. b. are held together by covalent bonds. c. are oriented in the same direction. d. are complementary to each other. MSugalski 8/7/06 4:42 PM Comment [1]: Delete Answer: d Hint: The strands in a DNA double helix have a specific relationship to each other. The structure of the DNA molecule can be reviewed in section 9.2 in your textbook. a. Incorrect. The two strands have a specific relationship but are not identical to each other. b. Incorrect. Covalent bonds are involved in forming the sugar-phosphate backbone of the strand but are not found between the bases on opposite strands. c. Incorrect. The two strands run in opposite directions. d. Correct. Base-pairing between the two strands ensures that the two strands are complementary to each other. (F)5. Consider the backbone of the DNA double helix. Which statement is NOT true? a. It is composed of alternating sugar and phosphate groups. b. The backbone is not straight, but twisted. c. The DNA backbone forms the central core of the DNA molecule. d. There is directionality to the backbone. Hint: The backbone of the DNA molecule has a regular structure. The structure of the DNA molecule can be reviewed in section 9.2 in your textbook. a. Incorrect. Each strand has a sugar-phosphate backbone. b. Incorrect. Since the entire DNA molecule is twisted, the backbones must be twisted as well. c. Correct. The sugar-phosphate backbones are on the outside of the DNA molecule. d. Incorrect. The DNA strand has directionality. One end of the DNA molecule has a free phosphate group; the other has a free sugar group (F)6. The sugars and phosphates in the "backbone" of a DNA strand are held together by. a. covalent bonds b. hydrogen bonds c. ionic bonds

8 Hint: The types of bonds are important in DNA structure and replication. Please review section 9.2 of your text. a. Correct. The DNA backbone is held together by strong covalent bonds in which the phosphorus of the phosphate group and the oxygen of the sugar share electrons. b. Incorrect. Hydrogen bonds are important in DNA structure but don t hold the sugars and phosphates together. c. Incorrect. Ionic bonds are not involved in DNA structure. (F)7. The two strands of a DNA double helix are held together by. a. covalent bonds between the sugars of one nucleotide and the phosphates of the adjacent nucleotide b. hydrogen bonds between bases on opposite DNA strands c. ionic bonds between DNA and water Hint: The types of bonds are important in DNA structure and replication. Please review section 9.2 of your text. a. Incorrect. The nucleotides in an individual DNA strand, not the two strands themselves, are held together by these bonds. b. Correct. The two DNA strands are held together by hydrogen bonds between complementary bases in the two DNA strands. c. Incorrect. Ionic bonds are not involved in DNA structures. (F)8. Which of the following lists the correct order of events in DNA replication? a. Enzymes unwind the DNA double helix; DNA polymerase makes two new DNA strands complementary to the old ones; the two DNA molecules wind up into a double helix with one new strand and one old strand. b. Two DNA molecules wind up into a double helix with one new strand and one old strand; DNA polymerase makes two new DNA strands complementary to the old ones; enzymes unwind the DNA double helix. c. DNA polymerase makes the new DNA strands complementary to the old ones; enzymes unwind the DNA double helix; the two DNA molecules wind up into a double helix with one new strand and one old strand. Hint: The events in DNA replication follow a logical sequence. Please review section 9.4 of the text. a. Correct. The original helix unwinds, two new strands are made, and two helices are produced. b. Incorrect. If the DNA molecules wind together first, the enzymes cannot access the bases to replicate the strands. c. Incorrect. DNA polymerase cannot access the bases of DNA molecules that are wound together. (F)9. Which of the following events occur within a DNA replication bubble? a. DNA polymerase helps to break hydrogen bonds between complementary base pairs. b. DNA helicase attaches the phosphate of a free nucleotide to the sugar of the previous nucleotide in the daughter strand. c. DNA helicase unwinds the double helix at each replication fork within a replication bubble. d. none of the above Hint: The names of the enzymes give a clue to their function. See section 9.4 of your textbook.

9 a. Incorrect. This is a function of DNA helicase. b. Incorrect. This is a function of DNA polymerase. c. Correct. Helicase first must unwind and break apart the parent helix so that the DNA polymerase can gain access to the bases as a template for building the new strand. d. Incorrect. One of the above answers is true. (C)10. Which of the following options would result from the actions of DNA polymerase during DNA replication? a. Two DNA polymerase molecules act to synthesize a long continuous daughter DNA strand from each parental strand; ligase is not needed. b. Two DNA polymerase molecules act to synthesize a short segment of daughter DNA from each parental strand; ligase is used to connect these short segments of both daughter strands. c. Two DNA polymerase molecules act to synthesize daughter DNA strands: one via a long continuous strand that moves in the same direction as the helicase, and a second polymerase synthesizes short segments of DNA that must be joined by ligase. d. none of the above Hint: Recall how DNA polymerase operates, and apply this knowledge to the fact that the two strands of a DNA helix are oriented in opposite directions. See section 9.4 of your textbook. a. Incorrect. Because the parental DNA strands are oriented in opposite directions, only one daughter strand is synthesized as a continuous strand. b. Incorrect. Because the parental DNA strands are oriented in opposite directions, only one daughter strand is synthesized in repeating segments. c. Correct. The disjointed short segments must be joined by ligase to form a complete daughter DNA strand. d. Incorrect. There is one correct answer. (F)11. Replication bubbles: a. consist of one moving replication fork and one fixed replication fork. b. are always shrinking in size. c. are only present once per chromosome. d. consist of two replication forks moving in opposite directions. Answer: d Hint: Replication bubbles are where new DNA is being synthesized. DNA replication is discussed in section 9.4 in your textbook. a. Incorrect. Both replication forks are moving as replication is occurring. b. Incorrect. Replication bubbles are always growing in size c. Incorrect. In eukaryotes, many replication bubbles are found on each chromosome. d. Correct. The two forks of the bubble will be moving in opposite directions so that each bubble will increase in size. (C)12. The correct nucleotides to be added to the new DNA strand are determined by: a. DNA ligase. b. base pairing between the free nucleotides and bases on the template strand. c. DNA helicase. d. base pairing between the free nucleotides and bases on the new DNA strand.

10 Hint: Think about a specific relationship you learned about DNA structure. DNA replication is discussed in section 9.4 in your textbook. a. Incorrect. DNA ligase is responsible for putting together stretches of DNA strands, not for adding individual nucleotides to a growing chain. b. Correct. Standard base pairing rules determine the next nucleotide to add to the chain. c. Incorrect. DNA helicase is responsible for unwinding of the DNA double helix. d. Incorrect. The sequence of nucleotides on the new DNA strand is not determined by other nucleotides on the same strand. (C)13. DNA replication is a semiconservative process because: a. each of the resulting DNA double helices will consist of one newly synthesized strand and one parental strand. b. the resulting DNA molecules will consist of one with two newly synthesized strands, and the other will contain the original parental strands. c. the nucleotides from other nucleic acids are constantly being recycled to make new nucleic acids. d. each resulting DNA molecule will contain short stretches of newly synthesized DNA interspersed with the original parental DNA. Hint: DNA replication and its role in cell division are covered in section 9.4. a. Correct. Each of the parental strands will serve as a template for making a complementary strand. These will stay together to form a helix. b. Incorrect. This does not coincide with semiconservative replication. c. Incorrect. Although this statement is true, semiconservative replication does not refer to this strategy. d. Incorrect. This type of replication is not seen with DNA. (F)14. What is the approximate error rate for DNA replication? a. one error for every thousand nucleotides b. one error for every million nucleotides c. one error for every billion nucleotides Hint: DNA replication is more accurate than expected based on the error rate of DNA polymerase. See section 9.5 in your textbook. a. Incorrect. The error rate is much lower than this. b. Incorrect. The error rate is much lower than this. c. Correct. During DNA replication the DNA polymerase makes approximately 1 error in every 10, 000 base pairs, but proofreading enzymes help to correct many of these, reducing the error rate of DNA replication. (F)15. Which of the following can be caused by ultraviolet radiation in sunlight? a. Adjacent thymines become linked together. b. The DNA molecule is degraded from each end. c. DNA molecule becomes fragmented. d. All of the above can happen. Hint: Ultraviolet radiation is one of the important causes of damage to DNA. See section 9.5 for more

11 information. a. Correct. This is the most important manner by which UV light damages DNA. b. Incorrect. This usually occurs whether UV light is present or not. c. Incorrect. This does not usually happen to DNA exposed to sunlight. d. Incorrect. Only one of the above will typically happen when your cells are exposed to UV light.