Exam #4: Ch.16, 17, 18, 19 & 21

1) In a nucleosome, the DNA is wrapped around ________.

A) a thymine dimer

B) histones

C) polymerase molecules

D) ribosomes

B) histones

2) Which of the following types of molecules help to hold the DNA strands apart while they are being replicated? 2)

_______

A) DNA polymerase

B) primase

C) single-strand DNA binding proteins

D) ligase

C) single-strand DNA binding proteins

3) Which of the following statements correctly describes the structure of chromatin? 3) _______

A) Heterochromatin is composed of DNA, whereas euchromatin is made of DNA and RNA.

B) Euchromatin is not transcribed, whereas heterochromatin is transcribed.

C) Both heterochromatin and euchromatin are found in the cytoplasm.

D) Heterochromatin is highly condensed, whereas euchromatin is less compact.

D) Heterochromatin is highly condensed, whereas euchromatin is less compact.

4) Which of the following statements accurately describes the structure of a eukaryotic chromosome? 4) _______

A) It is a single linear molecule of double-stranded DNA plus proteins.

B) It has different numbers of genes in different cell types of an organism.

C) It is constructed as a series of nucleosomes wrapped around two DNA molecules.

D) It is composed of a single strand of DNA.

A) It is a single linear molecule of double-stranded DNA plus proteins.

5) Telomere shortening puts a limit on the number of times a cell can divide. Research has shown that telomerase can extend

the life span of cultured human cells. Which of the following best explains the effect of telomerase on cellular aging? 5)

_______

A) Telomerase shortens telomeres, which delays cellular aging.

B) Telomerase would have no effect on cellular aging.

C) Telomerase will speed up the rate of cell proliferation.

D) Telomerase can eliminate telomere shortening and slows aging

D) Telomerase can eliminate telomere shortening and slows aging

6) The elongation of the leading strand during DNA synthesis ________. 6) _______

A) progresses away from the replication fork

B) produces Okazaki fragments

C) occurs in the 3' 5' direction

D) depends on the action of DNA polymerase

D) depends on the action of DNA polymerase

7) Within a double-stranded DNA molecule, if adenine forms hydrogen bonds with thymine, and cytosine forms hydrogen

bonds with guanine what consequence in the structure of the DNA? 7) _______

A) It permits complementary base pairing.

B) It determines the type of protein produced.

C) It allows variable width of the double helix.

D) It determines the tertiary structure of a DNA molecule.

A) It permits complementary base pairing.

8) In bacteria, what is the function of DNA polymerase III? 8) _______

A) to add nucleotides to the 3' end of a growing DNA strand

B) to degrade damaged DNA molecules

C) to seal together the broken ends of DNA strands

D) to unwind the DNA helix during replication

A) to add nucleotides to the 3' end of a growing DNA strand

9) A phosphorescent red strain of bacteria is heat-killed and mixed with a living, colorless strain. Further observations of the mixture show that some of the living cells are now red. Which of the following observations would provide the best evidence that red color is a heritable trait? 9) _______

A) especially bright red color in some members of the living strain

B) when the heat-killed and living cells are mixed there is a decrease in the overall amount of red color

C) after a few generations there are no more colorless cells, all cells are red

D) as the living cells divide the number of red cells increases

D) as the living cells divide the number of red cells increases

10) In his work with pneumonia-causing bacteria and mice, Griffith found that ________. 10) ______

A) heat-killed pathogenic cells caused pneumonia

B) the polysaccharide coat of bacteria caused pneumonia

C) some substance from pathogenic cells was transferred to nonpathogenic cells, making them pathogenic

D) the protein coat from pathogenic cells was able to transform nonpathogenic cells

C) some substance from pathogenic cells was transferred to nonpathogenic cells, making them pathogenic

11) Which of the following is most likely to result if a cell is unable to produce histone proteins? 11) ______

A) there would be an increase in the amount of DNA produced during replication

B) topoisomerases in the 300-nm fiber scaffolding would not need to be as active

C) the 30-nm fiber pack more tightly and become thinner than 30 nm

D) the cell's DNA could not be packed into its nucleus

D) the cell's DNA could not be packed into its nucleus

12) In DNA polymerization, a phosphodiester bond is formed between a phosphate group of the nucleotide being added and which of the following atoms or molecules of the last nucleotide in the polymer? 12) ______

A) a nitrogen from the nitrogen-containing base

B) C6

C) the 3' OH

D) the 5' phosphate

C) the 3' OH

13) Exposure to the UV radiation in sunlight causes DNA changes in skin cells. Why are these changes more harmful when they occur in an individual with xeroderma pigmentosum (XP) than in an individual who does not have this disorder?

A) Compared to XP individuals, non-XP individuals have more effective nucleotide excision repair enzymes.

B) XP individual's DNA replication machinery incorporates more incorrect nucleotides in new DNA strands than occur in non-

XP individuals.

C) XP individuals have significantly more thymine's in their DNA than non-XP individuals do

D) Compared to XP individuals, non-XP individuals produce more UV protecting pigments.

A) Compared to XP individuals, non-XP individuals have more effective nucleotide excision repair enzymes.

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

A) A = C

B) A + T = G + C

C) A + G = C + T

D) A = G

C) A + G = C + T

15) DNA is isolated from bacteria undergoing DNA replication. After heat treatment to disrupt H-bonds the DNA is centrifuged and it separates into two classes. One class of DNA includes very large molecules (thousands or even millions of nucleotides long), and the other includes short stretches of DNA (several hundred to a few thousand nucleotides in length). Which types of DNA do the two classes most likely represent?

A) Okazaki fragments and Origin of replication

B) leading strands and fragments generated due to replication errors

C) leading strands and Okazaki fragments

D) lagging strands and Okazaki fragments

C) leading strands and Okazaki fragments

16) In a healthy eukaryotic cell, the rate of DNA repair is typically equal to the rate of DNA mutation. Which of the following is

most likely to result if the rate of repair lags behind the rate of mutation? 16) ______

A) DNA replication will proceed more quickly

B) RNA may be used instead of DNA as inheritance material

C) DNA replication will continue by a new mechanism

D) the cell can be transformed into a cancerous cell

D) the cell can be transformed into a cancerous cell

17) Which of the following characteristics allowed Hershey and Chase to determine whether the genetic material was made of DNA or protein?

A) DNA contains phosphorus, whereas protein does not.

B) DNA contains nitrogen, whereas protein does not.

C) DNA contains sulfur, whereas protein does not.

D) DNA contains purines, whereas protein includes pyrimidines.

A) DNA contains phosphorus, whereas protein does not.

18) Rosalind Franklin's X-ray crystallography data suggested DNA is double stranded and has a uniform diameter. These observations can be used to rule out base pairing between two of the same nucleotide because ________.

A) thymine dimers are removed by excision repair

B) the antiparallel orientation of strands would result in one of the pair being upside down

C) an A-A pair is wider than a C-C pair

D) identical nucleotides would not have the appropriate number of hydrogen bonding sites to pai

C) an A-A pair is wider than a C-C pair

19) Which list the provides the correct enzyme order required for nucleotide excision repair of a thymine dimer?

 A) helicase, DNA polymerase, DNA ligase

B) DNA ligase, nuclease, helicase

C) nuclease, DNA polymerase, DNA ligase

D) nuclease, DNA polymerase, RNA primase

C) nuclease, DNA polymerase, DNA ligase

20) In E. coli, which enzyme catalyzes the elongation of a new DNA strand in the 5' → 3' direction?  20) ______

A) DNA polymerase III

B) helicase

C) primase        

D) DNA ligase

A) DNA polymerase III

21) Which of the following types of cells are affected most by telomere shortening?        21) ______

A) only animal cells       

B) only plant cells

C) only prokaryotic cells             

D) only eukaryotic cells

D) only eukaryotic cells

22) Which of the following statements correctly describes the difference between the leading strand and the lagging strand in DNA replication?   22) ______

A) The leading strand is synthesized in the 3'→ 5' direction in a discontinuous fashion, while the lagging strand is synthesized in the 5'→ 3' direction in a continuous fashion.

B) The leading strand requires an RNA primer, whereas the lagging strand does not.

C) There are different DNA polymerases involved in elongation of the leading strand and the lagging strand.

D) The leading strand is synthesized continuously in the 5'→ 3' direction, while the lagging strand is synthesized discontinuously in the 5'→ 3' direction.

D) The leading strand is synthesized continuously in the 5'→ 3' direction, while the lagging strand is synthesized discontinuously in the 5'→ 3' direction.

23) Use the figure to answer the following question.

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 "heavy" (radioactive) nitrogen (15N) for several generations and then transfer them to 14N medium. Which pattern in the figure would you expect if the DNA was replicated in a conservative manner? 

A) A     

B) B      

C) C     

D) D

B) B

24) Which of the following characteristics of DNA allows it to carry a vast amount of hereditary information?          24) ______

 

A) complementary pairing of bases          B) antiparallel orientation

C) sequence of bases       D) phosphate-sugar backbones

C) sequence of bases

25) Two students decided to repeat the Hershey and Chase experiment, with modifications. Like Hershey and Chase they used radioactive sulfur but they substituted radioactive nitrogen for radioactive phosphate. They reasoned that each nucleotide has only one phosphate and two to five nitrogen atoms. Thus, labeling the nitrogen atoms would provide a stronger signal than labeling the phosphates. Which of the following is the biggest shortcoming in their experimental design? 25) ______

A) The radioactivity would not distinguish between DNA and proteins because proteins contain nitrogen.

B) Radioactive nitrogen has a half-life of 100,000 years, therefore, the material would be too dangerous for too long.

C) There is no radioactive isotope of nitrogen.

D) The signal from the nucleotide would be so strong that it would overwhelm the signal from sulfur.

A) The radioactivity would not distinguish between DNA and proteins because proteins contain nitrogen.

26) A student 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? 26) ______

A) primase B) Okazaki fragments

C) DNA ligase D) DNA polymerase

C) DNA ligase

27) Which of the following combinations of base pairs will be found in a molecule of DNA? 27) ______

A) A + C = G + T

B) A = G and C = T

C) G + C = T + A

D) A = C

A) A + C = G + T

28) Researchers found a strain of bacteria that had mutation rates one hundred times higher than normal. Which of the following statements correctly describes the most likely cause of these results? 28) ______

A) The proofreading mechanism of DNA polymerase was not working properly.

B) The single-strand binding proteins were malfunctioning during DNA replication.

C) There were one or more base pair mismatches in the RNA primer.

D) The DNA polymerase was unable to add bases to the growing nucleic acid chain.

A) The proofreading mechanism of DNA polymerase was not working properly.

29) In DNA replication in E. coli, the enzyme primase is used to attach a 5 to 10 base ribonucleotide strand complementary to the parental DNA strand. The RNA strand serves as a starting point for the DNA polymerase that replicates the DNA. If a mutation occurred in the primase gene, which of the following results would you expect? 29) ______

A) Replication would not occur on either the leading or lagging strand.

B) Replication would only occur on the leading strand.

C) Replication would only occur on the lagging strand.

D) Replication would not be affected as the enzyme primase in involved with RNA synthesis.

A) Replication would not occur on either the leading or lagging strand.

30) In E. coli, a mutation in a gene called dnaB prevents the helicase from binding at the origin of replication. Which of the following events would you expect to occur as a result of this mutation? 30) ______

A) Additional proofreading will occur.

B) No replication fork will be formed.

C) Replication will require a DNA template from another source.

D) Replication will occur via RNA polymerase alone.

B) No replication fork will be formed.

31) A sample of double-stranded DNA contains 42% cytosine. Approximately what percent of the nucleotides in this sample will be thymine? 31) ______

A) 16%

B) 8%

C) 42%

D) 58%

B) 8%

32)Referring to the figure, what bases will be added as DNA replication proceeds on the bottom strand? 32) ______

A) 3′ T, C, T, G, C, T, G 5′

B) 3′ G, T, C, G, T, C, T 5′

C) 5′ C, A, G, C, A, G, A 3′

D) 5′ A, G, A, C, G, A, C 3′

D) 5′ A, G, A, C, G, A, C 3′

33) Which of the following statements correctly describes the difference between ATP used in metabolism and the nucleotides used as a building block during DNA synthesis? 33) ______

A) ATP is found only in human cells; the nucleotides are found in all animal and plant cells.

B) The nucleotides have the sugar deoxyribose; ATP has the sugar ribose.

C) ATP contains three high-energy bonds; the nucleotides have two.

D) The nucleotides have two phosphate groups; ATP has three phosphate groups.

B) The nucleotides have the sugar deoxyribose; ATP has the sugar ribose.

34) A sample of double-stranded DNA contains 28% thymine. Approximately what percent of the nucleotides in this sample will be guanine? 34) ______

A) 22%

B) 16%

C) 72%

D) 8%

A) 22%

35) Which of the following is most likely to result from reduced or very little active telomerase activity? 35) ______

A) Cells may become cancerous.

B) Cells maintain normal functioning.

C) Cells age and begin to lose function.

D) Telomere lengthens in germ cells.

C) Cells age and begin to lose function.

36) The sequence of nucleotides below is present at a DNA location where the chain opens to form a replication fork:

3' C C T A G G C T G C A A T C C 5'

An RNA primer is formed starting at the underlined T (T) of the template. Which of the following represents the primer sequence? 36) ______

A) 5' A C G U U A G G 3'

B) 5' A G C C T A G G 3'

C) 5' A G C C U A G G 3'

D) 5' A C G T T A G G 3'

A) 5' A C G U U A G G 3'

37) Which of the following is a reason that the low error rate of DNA replication is important to evolution? 37) ______

A) Rare errors are the source of variation.

B) Fixing replication errors provides a cellular role for mismatch repair enzymes.

C) Replication with a high error rate is likely to kill the cell.

D) Most mutations have no effect on phenotype.

A) Rare errors are the source of variation.

38) Which of the following structural characteristics is most critical for the association between histones and DNA?

A) Histones are positively charged.

B) Histones are highly conserved (that is, histones are very similar in every eukaryote).

C) There are at least five different histone proteins in every eukaryote.

D) Histones are small proteins

A) Histones are positively charged.

39) Which of the following statements describes the process of transformation in bacteria?

A) External DNA is taken into a cell, becoming part of the cell's genome.

B) A strand of RNA is created from a DNA molecule.

C) A strand of DNA is created from an RNA molecule.

D) Bacterial cells are infected by a phage DNA molecule

A) External DNA is taken into a cell, becoming part of the cell's genome.

40) Who performed classic experiments that supported the semiconservative model of DNA replication? 40) ______

A) Franklin and Wilkins

B) Watson and Crick

C) Meselson and Stahl

D) Hershey and Chase

C) Meselson and Stahl

41) What are telomeres? 41) ______

A) enzymes that elongate the DNA strand during replication

B) the sites of origin of DNA replication

C) the ends of linear chromosomes

D) the structures that hold two sister chromatids together

C) the ends of linear chromosomes

42) Histone proteins contain internal cores that are hydrophobic and surface amino acids that are positively charged. Which of the following characteristics of DNA would best support tight binding between DNA and histones?

A) the DNA backbone has a net negative charge that forms ionic bonds with histones

B) the ring structures in DNA bases that disperse charge promote hydrophobic interactions with histone cores

C) DNA 5' and 3' ends have negative charge responsible for stabilizing interactions with histone surfaces

D) the 3.4 nm per helical turn in DNA fits around the spherical shape of the histones

B) the ring structures in DNA bases that disperse charge promote hydrophobic interactions with histone cores

43) Frederick Griffith heat-killed a culture of pathogenic bacteria. He split the sample and injected half of it into mice. The mice lived. He then mixed the other half with a living, nonpathogenic bacteria strain and injected the mixture into mice. The mice died. These results best support which of the following conclusions.43) ______

A) splitting the culture revived the pathogenic bacteria

B) a substance had been transferred from pathogenic to nonpathogenic bacteria

C) the initial heat treatment was unsuccessful

D) non-pathogenic bacteria were transformed by pathogenic capsule proteins

B) a substance had been transferred from pathogenic to nonpathogenic bacteria

44) Which of the following investigators was (were) responsible for determining that DNA contains equal amounts of adenine and thymine, and equal amounts of guanine and cytosine?

A) Matthew Meselson and Franklin Stahl

B) Erwin Chargaff

C) Oswald Avery, Maclyn McCarty, and Colin MacLeod

D) Alfred Hershey and Martha Chase

B) Erwin Chargaff

45) Which of the following is a reason that a new DNA strand elongates only in the 5' to 3' direction during DNA replication?

A) Replication must progress toward the replication fork.

B) Dehydration reactions require a free -OH group.

C) DNA polymerase begins adding nucleotides at the 3' end of the template.

D) Single stranded binding protein stabilizes DNA by blocking access to the 5' end.

B) Dehydration reactions require a free -OH group.

46) What is the role of DNA ligase in the elongation of the lagging strand during DNA replication? 46) ______

A) It joins Okazaki fragments together.

B) It unwinds the parental double helix.

C) It stabilizes the unwound parental DNA.

D) It synthesizes RNA nucleotides to make a primer

A) It joins Okazaki fragments together.

47) What is the function of the enzyme topoisomerase in DNA replication?

A) building RNA primers using the parental DNA strand as a template

B) detecting the shape of the template base's surface to help recruit the appropriate nucleotide to pair

C) reattaching the hydrogen bonds between the base pairs in the double helix

D) relieving strain in the DNA ahead of the replication fork caused by the untwisting of the double helix

D) relieving strain in the DNA ahead of the replication fork caused by the untwisting of the double helix

48) Which of the following statements correctly describes the difference between the leading and the lagging strands of DNA in DNA replication? 48) ______

A) The lagging strand is synthesized continuously, whereas the leading strand is synthesized in short fragments that are

ultimately stitched together.

B) The leading strand is synthesized by adding nucleotides to the 3' end of the growing strand, and the lagging strand is

synthesized by adding nucleotides to the 5' end.

C) The leading strand is synthesized at twice the rate of the lagging strand.

D) The leading strand is synthesized in the same direction as the movement of the replication fork, and the lagging strand is synthesized in the opposite direction.

D) The leading strand is synthesized in the same direction as the movement of the replication fork, and the lagging strand is synthesized in the opposite direction.

49) The spontaneous loss of amino groups from adenine in DNA results in hypoxanthine, an uncommon base, opposite thymine. What combination of proteins could repair such damage?

A) telomerase, primase, DNA polymerase

B) telomerase, helicase, single-strand binding protein

C) DNA ligase, replication fork proteins, adenylyl cyclase

D) nuclease, DNA polymerase, DNA ligase

D) nuclease, DNA polymerase, DNA ligase

50) Which of the following statements accurately describes differences between DNA replication in prokaryotes and DNA replication in eukaryotes?

A) Prokaryotic chromosomes have histones, whereas eukaryotic chromosomes do not.

B) Prokaryotic chromosomes have a single origin of replication, whereas eukaryotic chromosomes have many.

C) Prokaryotes produce Okazaki fragments during DNA replication, but eukaryotes do not.

D) The rate of elongation during DNA replication is slower in prokaryotes than in eukaryotes.

B) Prokaryotic chromosomes have a single origin of replication, whereas eukaryotic chromosomes have many.

51) What is the basis for the difference in how the leading and lagging strands of DNA molecules are synthesized?

A) The The origins of replication occur only at the 5' end.

B) DNA polymerase can join new nucleotides only to the 3' end of a pre-existing strand, and the strands are antiparallel.

C) Helicases and single-strand binding proteins work at the 5' end.

D) DNA ligase works only in the 3' → 5' direction.

B) DNA polymerase can join new nucleotides only to the 3' end of a pre-existing strand, and the strands are antiparallel.

52) DNA strands are antiparallel. Which of the following statements defines "antiparallel"?

A) Hydrogen bonds between base pairs cause DNA strands to cross.

B) A 5' to 3' DNA strand is paired with the 3' to 5' DNA strand.

C) The double helix structure of DNA creates nonparallel strands.

D) One DNA strand contains bases that complement the bases in the opposite strand.

B) A 5' to 3' DNA strand is paired with the 3' to 5' DNA strand.

53) Which answer best describes the role of telomerase in replicating the ends of linear chromosomes? 53) ______

A) It adds numerous GC pairs, which resist hydrolysis and maintain chromosome integrity.

B) It adds a 5' cap structure to the chromosome ends that resists degradation by nucleases.

C) It catalyzes the lengthening of telomeres, compensating for the shortening that could occur during replication without telomerase activity.

D) It causes specific double-strand DNA breaks that result in blunt ends on both strands.

C) It catalyzes the lengthening of telomeres, compensating for the shortening that could occur during replication without telomerase activity

54) E. coli cells grown on 15N medium are transferred to14N 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? 54) ______

A) one high-density and one low-density band

B) one intermediate-density band

C) one low-density and one intermediate-density band

D) one high-density and one intermediate-density band

C) one low-density and one intermediate-density band

55) Hershey and Chase set out to determine which type of molecule is used for genetic inheritance. They completed a series of experiments where E. coli was infected by a T2 virus. Which molecular component of the T2 virus ended up inside the cell?

A) DNA

B) ribosome

C) RNA

D) protein

A) DNA

56) Semiconservative replication involves a template. Which of the following best describes the template molecule?

A) one strand of the DNA molecule

B) single-stranded binding proteins

C) DNA polymerase

D) an RNA molecule

A) one strand of the DNA molecule

57) In the late 1950s, Meselson and Stahl grew bacteria in a medium containing "heavy" (radioactive) nitrogen (15N) and then transferred them to a medium containing 14N (non-radioactive). Which of the results in the figure would be expected after one round of DNA replication in the presence of 14N?

A) A

B) B

C) C

D) D

D) D

58) Radioactive thymine is added to media containing one actively dividing E. coli bacterium. Which of the following outcomes would be seen after a single cell division?

A) One of the daughter cells, but not the other, would have radioactive DNA.

B) Neither of the two daughter cells would be radioactive.

C) DNA in both daughter cells would be radioactive.

D) All four bases of the DNA would be radioactive.

C) DNA in both daughter cells would be radioactive.

59) After DNA replication, the resulting daughter DNA double helix contains one strand of the original parental DNA and one new strand. What is the explanation for this phenomenon?

A) DNA replication is not conservative.

B) DNA replication is semiconservative.

C) DNA replication is conservative.

D) RNA synthesis is conservative.

B) DNA replication is semiconservative.

60) The lagging strand is characterized by a series of short segments of DNA (Okazaki fragments) that are joined together to form a finished lagging strand. The experiments that led to the discovery of Okazaki fragments gave evidence for which of the following ideas? 60) ______

A) DNA is the genetic material that requires removal of short RNA segments to be functional.

B) DNA polymerase synthesizes leading and lagging strands during replication only in one direction.

C) DNA is a polymer consisting of four monomers: adenine, thymine, guanine, and cytosine.

D) Bacterial replication is fundamentally different from eukaryotic replication.

B) DNA polymerase synthesizes leading and lagging strands during replication only in one direction.

61) An mRNA molecule with the sequence 5′-CCG-ACG-3′is being translated at a ribosome. The following charged transfer RNA molecules (with their anticodons shown in the 3′ to 5′ direction) are available. Two of them can correctly match the mRNA so that a dipeptide can form.

Which of the following dipeptides will form from this mRNA?

A) cysteine-alanine

B) alanine-alanine

C) glycine-cysteine

D) proline-threonine

D) proline-threonine

62) During the elongation phase of translation, which site in the ribosome represents the first location where a codon pairs with an anticodon? 62) ______

A) P site

B) E site

C) the large ribosomal subunit

D) A site

D) A site

63) Which of the following statements best supports the one gene-one enzyme hypothesis? 63) ______

A) A mutation in a single gene can result in a defective protein.

B) Sickle-cell anemia results in normal hemoglobin.

C) Alkaptonuria results when individuals lack multiple enzymes involved in the catalysis of homogentisic acid.

D) Multiple antibody genes can code for different related proteins, depending on the splicing that takes place post-transcriptionally.

A) A mutation in a single gene can result in a defective protein.

64) A single base substitution mutation is likely to have a less harmful effect when the base change results in which of the following? 64) ______

A) an amino acid substitution at the active site of an enzyme

B) an amino acid substitution that alters the tertiary structure of the protein

C) a stop codon

D) a codon that specifies the same amino acid as the original codon

D) a codon that specifies the same amino acid as the original codon

65) Once researchers identified DNA as the molecule responsible for transmitting heritable traits, they asked how information was transferred from the DNA in the nucleus to the site of protein synthesis in the cytoplasm. Which of the following statements correctly describes the mechanism of information transfer that accomplishes this task in eukaryotes?

A) RNA polymerase transfers information from the nucleus to tRNA synthase in the cytoplasm, where protein synthesis takes place.

B) DNA from a single gene is replicated and transferred to the cytoplasm, where it serves as a template for protein synthesis.

C) Transfer RNA takes information from DNA directly to a ribosome, where protein synthesis takes place.

D) Messenger RNA is transcribed from a single gene and transfers information to the cytoplasm, where protein synthesis takes place.

D) Messenger RNA is transcribed from a single gene and transfers information to the cytoplasm, where protein synthesis takes place.

66) Which of the following changes in an exon is most likely to result in a nonfunctional protein product? 66) ______

A) a codon deletion

B) a substitution in the last base of a codon

C) a base-pair deletion

D) an addition of three nucleotides

C) a base-pair deletion

67) In eukaryotes which of the following is the first step in translation? 67) ______

A) base pairing of activated methionine-tRNA to AUG of the messenger RNA

B) the small subunit of the ribosome recognizes and attaches to the 5′ cap of mRNA

C) the ribosome reaches a stop codon

D) binding of the larger ribosomal subunit to smaller ribosomal subunits

B) the small subunit of the ribosome recognizes and attaches to the 5′ cap of mRNA

68) A section of DNA has the base sequence shown in #1. A mutation in this DNA strand results in the base sequence shown in #2. What type of mutation does this change represent?

#1 5' - AGCGTTACCGT-3'

#2 5'-AGGCGTTACCGT-3'

A) a missense mutation

B) a silent mutation

C) frameshift mutation

D) a point mutation

C) frameshift mutation

69) A particular triplet of bases in the coding sequence of DNA is 5'-AAA-3'. The anticodon on the tRNA that binds the mRNA codon is ________.

A) 5′-UUA-3′

B) 5′-TTT-3′

C) 3′-UUU-5′

D) 3′-AAA-5′

D) 3′-AAA-5′

70) Which answer correctly compares prokaryotic and eukaryotic codons?

A) Prokaryotic codons usually specify different amino acids than those of eukaryotes.

B) Organism within a phylum share codons that are distinct from organisms in other phyla.

C) Organisms utilize codons that are nearly universal among all organisms.

D) Prokaryotic codons usually contain different bases than those of eukaryotes

C) Organisms utilize codons that are nearly universal among all organisms.

71) The genetic code is essentially the same for all organisms. From this, one can logically assume which of the following statements to be true?

A) DNA was the first genetic material.

B) Different organisms have different types of amino acids.

C) The same codons in different organisms translate into different amino acids.

D) A gene from an organism can theoretically be expressed by any other organism.

D) A gene from an organism can theoretically be expressed by any other organism.

72) The most commonly occurring mutation in people with cystic fibrosis is a deletion of a single codon. What is the result of this type of mutation?

A) a base-pair substitution

B) a polypeptide missing an amino acid

C) a polypeptide missing its N-terminus

D) a frameshift mutation

B) a polypeptide missing an amino acid

73) Which of the following molecules directly participates in the process of translation?

A) mRNA, tRNA, and DNA

B) mRNA, tRNA, DNA, and rRNA

C) mRNA, tRNA, and rRNA

D) mRNA, DNA, and rRNA

C) mRNA, tRNA, and rRNA

74) Which of the following processes will occur at the exposed 3′ end of a tRNA molecule?

A) The small and large subunits of the ribosome will attach to the 3" end.

B) The 5′ cap of the mRNA will bind covalently.

C) The single stranded nucleotides (ACCA) will be removed to stabilize the tRNA.

D) An amino acid will bind covalently.

D) An amino acid will bind covalently.

75) Which of the following statements correctly describes a ribozyme? 75) ______

A) It is an RNA with catalytic activity.

B) It is a catalyst that uses RNA as a substrate.

C) It is an enzyme that catalyzes the association between the large and small ribosomal subunits.

D) It is an enzyme that synthesizes RNA as part of the transcription process.

A) It is an RNA with catalytic activity.

76) Which of the following processes occurs in prokaryotes but not in eukaryotes? 76) ______

A) simultaneous transcription and translation of the same mRNA

B) translation in the absence of a ribosome

C) translocation into the ER

D) removing introns from pre-RNA

A) simultaneous transcription and translation of the same mRNA

77) Which of the following properties is associated with a protein that will be secreted from a eukaryotic cell?

A) Its signal sequence must target it to the plasma membrane.

B) Its signal sequence must target it to the ER.

C) Its signal sequence must be cleaved off as the polypeptide enters the ER.

D) It must be translated by a ribosome that remains free within the cytosol

B) Its signal sequence must target it to the ER.

78) In the structure of many eukaryotic genes, individual exons parallel which of the following?

A) the number of start sites for transcription

B) the number of polypeptides making up the functional protein

C) the various domains of the protein product

D) the sequence of the intron that immediately precedes each exon

C) the various domains of the protein product

79) Which answer correctly compares the primary transcript in the nucleus of a eukaryotic cell with the functional mRNA?

A) the primary transcript is smaller than the mRNA

B) both the primary transcript and mRNA contain introns

C) the primary transcript is the same size as the mRNA

D) the primary transcript is larger than the mRNA

D) the primary transcript is larger than the mRNA

80) Which of the following is true of a codon?

A) It is the basic unit of protein structure.

B) It can code for more than one amino acid.

C) It can be either in DNA or in RNA.

D) It never codes for the same amino acid as another codon.

C) It can be either in DNA or in RNA.

81) Which of the following processes occurs as part of transcription? 81) ______

A) mRNA attaches to ribosomes

B) proteins are synthesized

C) RNA is synthesized

D) DNA is replicated

C) RNA is synthesized

82) Which of the following processes correctly describes alternative RNA splicing?

A) It can allow the production of proteins of different sizes and functions from a single mRNA.

B) It can allow the production of similar proteins from different RNAs.

C) It is a mechanism for increasing the rate of translation.

D) It increases the rate of transcription.

A) It can allow the production of proteins of different sizes and functions from a single mRNA.

83) A particular triplet of bases in the template strand of DNA is 5′-AGT-3′. What would be the corresponding codon for the mRNA that is transcribed?

A) 5′-UCA-3′

B) 5′-AGT-3′

C) 3′-ACU-5′

D) 3′-UCA-5′

D) 3′-UCA-5′

84) Which of the following molecular structures contains codons?

A) mRNA

B) tRNA

C) rRNA

D) a protein

A) mRNA

85) The figure shows a simple metabolic pathway. According to Beadle and Tatum's hypothesis, how many genes are necessary for this pathway?

A) 3

B) 2

C) 5

D) It cannot be determined from the information provided.

B) 2

86) What amino acid sequence will be generated based on the following mRNA codon sequence?

5′-AUG-UCU-UCG-UUA-UCC-UUG-3′

A) Met-Arg-Glu-Arg-Glu-Arg

B) Met-Ser-Ser-Leu-Ser-Leu

C) Met-Glu-Arg-Arg-Glu-Leu

D) Met-Ser-Leu-Ser-Leu-Ser

B) Met-Ser-Ser-Leu-Ser-Leu

87) Using the CRISPR-Cas9 system to correct a genetic defect in a mouse brings with it which of the following risks?

A) increasing the animal's susceptibility to bacteriophage infection

B) decreasing the animal's ability to repair other mutations

C) altering non-target mouse genes needed for cell function

D) introducing CRISPR-Cas9 gene into the animal's genome

C) altering non-target mouse genes needed for cell function

88) Which of the following best describes the redundancy in the genetic code? 88) ______

A) The genetic code is different for different domains of organisms.

B) A single codon can specify the addition of more than one amino acid.

C) The genetic code is universal (the same for all organisms).

D) More than one codon can specify the addition of the same amino acid

D) More than one codon can specify the addition of the same amino acid

89) Refer to the metabolic pathway illustrated. If I, II, III, and IV are all required for growth, a bacterial strain that does not make enzyme X would be able to grow on medium supplemented with which of the following nutrient(s)?

A) nutrient A only

B) nutrient B only

C) nutrients A and B only

D) nutrients B, C, and D only

C) nutrients A and B only

90) The anticodon of a particular tRNA molecule is ________. 90) ______

A) the part of tRNA that bonds to a specific amino acid

B) catalytic, making the tRNA a ribozyme

C) complementary to the corresponding triplet in rRNA

D) complementary to the corresponding mRNA codon

D) complementary to the corresponding mRNA codon

91) Which of the following statements correctly describes Archibald Garrod's hypothesis for how "inborn errors of metabolism" such as alkaptonuria occur?

A) Enzymes are made of DNA, and affected individuals lack DNA polymerase.

B) Metabolic enzymes require vitamin cofactors, and affected individuals have significant nutritional deficiencies.

C) Certain metabolic reactions are carried out by ribozymes, and affected individuals lack key splicing factors.

D) Genes dictate the production of specific enzymes, and affected individuals have genetic defects that cause them to lack certain enzymes.

D) Genes dictate the production of specific enzymes, and affected individuals have genetic defects that cause them to lack certain enzymes.

92) In eukaryotic cells, transcription cannot begin until ________.

A) the 5' caps are removed from the mRNA

B) the two DNA strands have completely separated and exposed the promoter

C) the DNA introns are removed from the template

D) several transcription factors have bound to the promoter

D) several transcription factors have bound to the promoter

93) Which of the following molecules carries information from DNA and directs incorporation of amino acids at the ribosome?

A) tRNA

B) enzymes

C) rRNA

D) mRNA

D) mRNA

94) Which of the following statements is true about protein synthesis in prokaryotes? 94) ______

A) Translation requires no initiation or elongation factors.

B) Translation can begin while transcription is still in progress.

C) Extensive RNA processing is required before transcripts can be translated.

D) Protein targeting to cellular organelles requires recognition of signal sequences

B) Translation can begin while transcription is still in progress.

95) Which of the following statements describes the effect of a nonsense mutation on a gene?

A) It alters the reading frame of the mRNA.

B) It changes only one amino acid in the encoded protein.

C) It introduces a premature stop codon into the mRNA.

D) It has no effect on the amino acid sequence of the encoded protein.

C) It introduces a premature stop codon into the mRNA.

96) Two mRNAs (mRNA X and mRNA Y) are synthesized with the same exon sequences but poly-A tails of very different lengths. mRNA X is 7,500 bases long. mRNA Y is 6,900 bases long. The mRNA's are added to separate in vitro translation mixtures containing radioactive methionine and the reactions are allowed to proceed for 30 minutes. When the mixtures are analyzed, which of the following outcomes will most likely occur?

A) The radioactive proteins in the mRNA X mixture will begin with methionine while those in the mRNA Y mixture will not.

B) The radioactive proteins in the mRNA X mixture will be larger in size than those in the mRNA Y mixture.

C) The mRNA X mixture will contain radioactive proteins but the mRNA Y mixture will not.

D) The mRNA X mixture will contain more radioactive proteins than the mRNA Y mixture

D) The mRNA X mixture will contain more radioactive proteins than the mRNA Y mixture

97) What is the function of the release factor during translation in eukaryotes?

A) It binds to the stop codon in the A site in place of a tRNA.

B) It supplies a source of energy for termination of translation.

C) It releases the amino acid from its tRNA to allow the amino acid to form a peptide bond.

D) It releases the ribosome from the ER to allow polypeptides into the cytosol.

A) It binds to the stop codon in the A site in place of a tRNA.

98) Which of the following structures is needed for the translation initiation complex to form in eukaryotes?

A) 5′ AUG 3′

B) promoter

C) exon

D) 5′ cap

D) 5′ cap

99) Which of the following is most likely to occur if a researcher removes the 5′ cap and poly-A tail of an mRNA and inserts the mRNA molecule into a eukaryotic cell?

A) The mRNA will attaches to a ribosome and be translated, but more slowly.

B) The mRNA will be quickly converted into a ribosomal subunit.

C) The molecule will be degraded by enzymes.

D) The cell will add a new poly-A tail to the mRNA

C) The molecule will be degraded by enzymes.

100) Which of the following characteristics of gene expression is shared by eukaryotic and prokaryotic cells?

A) Signal sequences are needed for the production of membrane proteins.

B) Translation occurs before transcription.

C) Transcription of an mRNA is temporally separated from its translation.

D) Ribosomes attach to the plasma membrane when producing secreted proteins.

A) Signal sequences are needed for the production of membrane proteins.