Ch12 test file

Chapter 12: From DNA to Protein: Genotype to Phenotype

TEST FILE QUESTIONS

Multiple Choice

1. The toxin ricin can be fatal; it works by

a. breaking peptide bonds and destroying healthy proteins.

b. killing the cell by blocking protein synthesis.

c. blocking the synthesis of bacterial cell walls.

d. producing a lethal toxin that affects mRNA and ribosomal movement.

e. inhibiting the translocation of mRNA along the ribosome.

Textbook Reference: 12.0 Toxic Avenger at the Ribosome, p. 256

2. Genetic material is composed of

a. DNA.

b. amino acids.

c. ribose.

d. carbohydrates.

e. lipids.

Textbook Reference: 12.1 What Is the Evidence that Genes Code for Proteins? p. 257

3. The major phenotypic expression of genotype is in

a. proteins.

b. tRNA.

c. mRNA.

d. nucleic acids.

e. a mutation.


4. Which of the following are model organisms used in biological research?

a. Pea plants

b. Fruit flies

c. E. coli

d. Bread mold

e. All of the above


5. After irradiating Neurospora, Beadle and Tatum collected mutants that would

a. not grow on a minimal medium but would grow on a minimal medium with arginine.

b. grow on any minimal medium.

c. not grow on any minimal medium.

d. grow on a minimal medium but would not grow on a minimal medium with arginine.

e. None of the above


6. Within a group of mutants with the same growth requirement (i.e., the same overt

phenotype), mapping studies determined that individual mutations were on different

chromosomes. This indicates that

a. the same gene governs all the steps in a particular biological pathway.

b. different genes can govern different individual steps in the same biological pathway.

c. different genes govern the same step in a particular biological pathway.

d. all biological pathways are governed by different genes.

e. genes do not govern steps in biological pathways.


7. The study of Neurospora mutants grown on various supplemented media led to

a. a determination of the steps in biological pathways.

b. the “one-gene, one-enzyme” theory.

c. the idea that genes are “on” chromosomes.

d. Both a and b

e. Both a and c


8. Genes code for

a. enzymes.

b. polypeptides.

c. RNA.

d. All of the above



9. The classic work of Beadle and Tatum, later refined by others, provided evidence for

the

a. one-gene, one-enzyme hypothesis.

b. one-gene, one-polypeptide hypothesis.

c. mechanism by which information in genes is translated into traits.

d. effects of some mutations on organisms.

e. All of the above


10. How does RNA differ from DNA?

a. RNA contains uracil instead of thymine and it is usually single-stranded.

b. RNA contains uracil instead of thymine and it is usually double-stranded.

c. RNA contains thymine instead of uracil and it is usually single-stranded.

d. RNA contains uracil instead of cytosine.


Textbook Reference: 12.2 How Does Information Flow from Genes to Proteins? p. 260

11. Which of the following statements about the flow of genetic information is true?

a. Proteins encode information that is used to produce other proteins of the same amino

acid sequence.

b. RNA encodes information that is translated into DNA, and DNA encodes information

that is translated into proteins.

c. Proteins encode information that can be translated into RNA, and RNA encodes

information that can be transcribed into DNA.

d. DNA encodes information that is translated into RNA, and RNA encodes information

that is translated into proteins.



12. Which of the following molecules transfers information from the nucleus to the

cytoplasm?

a. DNA

b. mRNA

c. tRNA

d. Proteins

e. Lipids


13. The link between mRNA and a protein is

a. tRNA.

b. a promoter.

c. RNA polymerase.

d. DNA polymerase.

e. a start codon.


14. Which of the following molecules transfers information from mRNA to protein?

a. DNA

b. mRNA

c. tRNA

d. Proteins

e. Lipids


15. The “central dogma” of molecular biology states that

a. information flow between DNA, RNA, and protein is reversible.

b. information flow in the cell is unidirectional, from protein to RNA to DNA.

c. information flow in the cell is unidirectional, from DNA to RNA to protein.

d. the DNA sequence of a gene can be predicted if we know the amino acid sequence of

the protein it encodes.

e. the genetic code is ambiguous but not degenerate.


16. The adapters that allow translation of the four-letter nucleic acid language into the 20-

letter protein language are called

a. aminoacyl tRNA synthetases.

b. transfer RNAs.

c. ribosomal RNAs.

d. messenger RNAs.

e. ribosomes.


17. Which of the following does (do) not follow the “central dogma”?

a. Yeast

b. Onion cells

c. Bread mold

d. Skin cells

e. Retroviruses


18. Retroviruses do not follow the “central dogma” of DNARNAprotein because

they

a. contain RNA that is used to make DNA.

b. contain DNA that is used to make more RNA.

c. contain DNA that is used to make tRNA.

d. contain only RNA as the genetic material.

e. do not contain either DNA or RNA as the genetic material.


19. Viruses that violate the “central dogma” through the use of an enzyme that makes

DNA copies of an RNA molecule are called

a. bacteriophage.

b. retroviruses.

c. RNA viruses.

d. DNA viruses.

e. enveloped viruses.


20. Single-stranded RNA replicates by

a. making an RNA strand that is complementary to the original RNA strand.

b. using an adapter molecule.

c. the process of transcription.

d. the process of translation.

e. the process of reverse transcription.


21. Transcription is the process of

a. synthesizing a DNA molecule from an RNA template.

b. assembling ribonucleoside triphosphates into an RNA molecule without a template.

c. synthesizing an RNA molecule using a DNA template.

d. synthesizing a protein using information from a messenger RNA.

e. replicating a single-stranded DNA molecule.

Textbook Reference: 12.3 How Is the Information Content in DNA Transcribed to

Produce RNA? p. 261

22. The process of transcription synthesizes

a. transfer RNA.

b. messenger RNA.

c. ribosomal RNA.

d. proteins.

e. a, b, and c


Produce RNA? p. 261

23. The region of DNA in prokaryotes to which RNA polymerase binds most tightly is

the

a. promoter.

b. poly C center.

c. enhancer.

d. operator site.

e. minor groove.


Produce RNA? p. 262

24. Promoters are made of

a. proteins.

b. carbohydrates.

c. lipids.

d. nucleic acids.

e. amino acids.


Produce RNA? p. 262

25. A transcription start signal is called a(n)

a. initiation codon.

b. promoter.

c. origin.

d. operator.

e. nonsense codon.


Produce RNA? p. 262

26. RNA polymerase uses the _______ DNA template to synthesize a _______ mRNA.

a. 5’ to 3’; 5’ to 3’

b. 3’ to 5’; 3’ to 5’

c. 5’ to 3’; 3’ to 5’

d. 3’ to 5’; 5’ to 3’

e. Examples of all of the above have been found.


Produce RNA? p. 262

27. RNA polymerase is a(n)

a. RNA-directed DNA polymerase.

b. RNA-directed RNA polymerase.

c. DNA-directed RNA polymerase.

d. typical enzyme.

e. form of RNA.


Produce RNA? p. 262

28. The direction of synthesis for a new mRNA molecule is _______ from a _______

template strand.

a. 5’ to 3’; 5’ to 3’

b. 5’ to 3’; 3’ to 5’

c. 3’ to 5’; 5’ to 3’

d. 3’ to 5’; 3’ to 5’

e. 5’ to 5’; 3’ to 3’


Produce RNA? p. 262

29. The error rate for RNA polymerase is _______ that for most DNA polymerases.

a. less than

b. equal to

c. greater than

d. greater for frame shifts but less for base substitutions than

e. greater for base substitutions but less for frame shifts than


Produce RNA? p. 262

30. The process of transcription requires

a. a temporary stopping of DNA replication.

b. a temporary separation of the strands in the DNA template.

c. destruction of one of the strands of the DNA template.

d. relaxation of positive supercoils in the DNA template.

e. induction of positive supercoils in the DNA template.


Produce RNA? p. 262

31. DNA is composed of two strands, only one of which typically is used as a template

for RNA synthesis. By what mechanism is the correct strand chosen?

a. Both strands are tried and the one that works is remembered.

b. Only one strand has the start codon.

c. The promoter acts to aim the RNA polymerase.

d. A start factor informs the system.

e. It is chosen randomly.


Produce RNA? p. 262

32. There are differences in the amount of transcription that takes place for different

genes. One reason for these differences is that

a. some promoters are more effective at transcription initiation.

b. longer genes take longer to transcribe.

c. the outcome is influenced by random chance.

d. ribosomes tend to attach to transcripts even before transcription is completed.



Produce RNA? p. 262

33. Termination of transcription involves a

a. stop codon.

b. terminator sequence.

c. termiproteator.

d. hairline slip.

e. series of As.


Produce RNA? p. 262

34. There are _______ different RNA polymerases in eukaryotes.

a. two

b. three

c. four

d. five

e. six


Produce RNA? p. 262

35. The termination of transcription is signaled by

a. the stop codon.

b. a sequence of nitrogenous bases.

c. a protein bound to a certain region of DNA.

d. rRNA.

e. tRNA.


Produce RNA? p. 262

36. In eukaryotes, there are _________ RNA polymerases that catalyze the synthesis of

RNA from DNA.

a. two

b. three

c. four

d. five

e. six


Produce RNA? p. 262

37. The stop codons code for

a. no amino acid.

b. methionine.

c. glycine.

d. halt enzyme.

e. DNA binding protein.


Produce RNA? p. 263

38. How can DNA, which is made up of only four different bases, encode the information

necessary to specify the workings of an entire organism?

a. DNA molecules are extremely long.

b. DNA molecules form codons of three bases that code for amino acids.

c. The genetic code is redundant but not ambiguous.

d. DNA can be replicated with low error rates.

e. All of the above


Produce RNA? p. 264

39. How many codons specify amino acids?

a. 20

b. 23

c. 45

d. 60

e. 61


Produce RNA? p. 264

40. The genetic code is best described as

a. redundant but not ambiguous.

b. ambiguous but not redundant.

c. both ambiguous and redundant.

d. neither ambiguous nor redundant.

e. nonsense.


Produce RNA? p. 264

41. The three codons in the genetic code that do not specify amino acids are called

a. missense codons.

b. start codons.

c. stop codons.

d. promoters.

e. initiator codons.


Produce RNA? p. 264

42. A template DNA strand has the following base sequence: 3’-GUC, CCA-5’. What

would be the corresponding mRNA sequence?

a. 3’-GUC, CCA-5’

b. 5’-GUC, CCA-5’

c. 3’-CAG, GGU-5’

d. 5’-CAG, GGU-3’

e. 5’-CAG, GGT-3’


Produce RNA? p. 264

43. Imagine that a novel life form is found deep within Earth’s crust. Evaluation of its

DNA yields no surprises. However, it is found that a codon for this life form is just two

bases in length. How many different amino acids could this organism be composed of?

a. 4

b. 8

c. 16

d. 32

e. 64


Produce RNA? p. 265

44. Poly uracil codes for

a. three different amino acids.

b. poly tryptophan.

c. mRNA.

d. a fatty acid.

e. phenylalanine.


Produce RNA? p. 265

45. What events must take place to ensure that the protein made is the one specified by

mRNA?

a. tRNA must read mRNA correctly.

b. tRNA must carry the amino acid that is correct for its reading of the mRNA.

c. covalent bonding between the base pairs must occur.

d. Both a and b

e. All of the above

Textbook Reference: 12.4 How Is RNA Translated into Proteins? p. 265

46. Fewer different tRNA molecules exist than might have been expected for the

complexity of its function. This is possible because

a. the third position of the codon does not have to pair conventionally.

b. the second position of the codon does not have to pair conventionally.

c. the anticodon does not have the conventional bases.

d. there are fewer amino acids than there are possible codons.

e. the code is degenerating.


47. A sequence of three RNA bases can function as a(n)

a. codon.

b. anticodon.

c. gene.

d. Both a and b

e. Both a and c


48. The difference between mRNA and tRNA is that

a. tRNA has a more elaborate three-dimensional structure.

b. tRNAs are usually much smaller than mRNAs.

c. mRNA carries amino acids.

d. Both a and b



49. How is it possible for single-stranded RNA to fold into complex shapes?

a. Phosphodiester linkages form between the phosphate and the sugar ribose.

b. Internal base pairings make this possible: adenine with uracil and cytosine with

guanine.

c. Uracil’s methyl group binds to adenine, spiraling the molecule.

d. The single strand “twists” around itself.

e. The RNA binds to proteins, creating a conformation (three-dimensional shape).


50. Which of the following statements about codons and anticodons is true?

a. The codon bonds covalently with the anticodon.

b. The base sequences are the same.

c. There are 64 codons and 61 anticodons.

d. Activating enzymes link codons and anticodons.

e. At contact, the codon and the anticodon are antiparallel to each other.


51. The conformation of tRNA is maintained by

a. peptide bonds.

b. hydrogen bonds.

c. disulfide bridges.

d. phosphodiester bonds.

e. glycosidic linkages.


52. Activating enzymes

a. are sometimes referred to as the second genetic code.

b. link the right tRNAs and amino acids.

c. are also known as aminoacyl-tRNA synthetases.

d. are specific for one amino acid.

e. All of the above


53. The energy for translation is derived from

a. ATP.

b. GTP.

c. ATP and GTP.

d. the phosphodiester linkages in the incorporated nucleoside triphosphates.

e. glucose.


54. The enzyme that charges the tRNA molecules with appropriate amino acids is

a. tRNA chargeatase.

b. amino tRNA chargeatase.

c. transcriptase.

d. aminoacyl-tRNA synthetase.



55. Ribosomes are a collection of _______ that are needed for _______.

a. small proteins; translation

b. proteins and small RNAs; translation

c. proteins and tRNAs; transcription

d. proteins and mRNAs; translation

e. mRNAs and tRNAs; translation


56. During translation initiation, the first site occupied by a charged tRNA is the

a. A site.

b. B site.

c. large subunit.

d. T site.

e. P site.


57. It is currently believed that the enzyme that catalyzes formation of the peptide bond

during translation is composed of

a. amino acids.

b. proteins.

c. carbohydrates.

d. RNA.

e. DNA.


58. During translation elongation, the existing polypeptide chain is transferred to

a. the tRNA occupying the A site.

b. the tRNA occupying the P site.

c. the ribosomal rRNA.

d. a signal recognition particle.



59. mRNA is synthesized in the _______ direction, which corresponds to the _______ of

the protein.

a. 5’ to 3’; N terminus to C terminus

b. 3’ to 5’; C terminus to N terminus

c. 5’ to 3’; C terminus to N terminus

d. 3’ to 5’; N terminus to C terminus

e. Examples of all of the above have been found.


60. Proteins are synthesized from the _______, in the _______ direction along the

mRNA.

a. N terminus to C terminus; 5’ to 3’

b. C terminus to N terminus; 5’ to 3’

c. C terminus to N terminus; 3’ to 5’

d. N terminus to C terminus; 3’ to 5’

e. N terminus to N terminus; 5’ to 5’


61. In protein synthesis, the endoplasmic reticulum

a. is the site where mRNA attaches.

b. is the site where all ribosomes bind.

c. is the site of translation of membrane-bound and exported proteins.

d. produces tRNAs.

e. brings together mRNA and tRNA.

Textbook Reference: 12.5 What Happens to Polypeptides after Translation? p. 273

62. Which of the following is the correct order of events by which a protein is delivered

to its cellular destination?

a. A signal sequence binds to a docking protein, a membrane channel is formed,

chaperonins unfold the protein, the protein enters the organelle, and the protein refolds.

b. A membrane channel is formed, a signal sequence binds to a docking protein,

chaperonins unfold the protein, the protein enters the organelle, and the protein refolds.

c. Chaperonins unfold the protein, a signal sequence binds to a docking protein, a

membrane channel is formed, the protein enters the organelle, and the protein refolds.

d. A membrane channel is formed, chaperonins unfold the protein, a signal sequence

binds to a docking protein, the protein enters the organelle, and the protein refolds.

e. A signal sequence binds to a docking protein, a transmembrane-gated channel opens,

and the protein enters the organelle.


63. In eukaryotes, ribosomes become associated with endoplasmic reticulum membranes

when

a. a signal sequence on the mRNA interacts with a receptor protein on the membrane.

b. a signal sequence on the ribosome interacts with a receptor protein on the membrane.

c. a signal sequence at the amino terminus of the protein being synthesized interacts with

a receptor protein on the ribosome.

d. a signal sequence on the protein being synthesized interacts with a signal recognition

particle and both bind to the endoplasmic reticulum.

e. the messenger RNA passes through a pore in the membrane.


64. The addition of sugar residues to the protein after translation is called

a. glycation.

b. glycosylation.

c. phosphorylation.

d. proteolysis.

e. exonuclease digestion.


65. After translation, some proteins are processed by _______, which is cleavage of the

protein to make a shortened finished protein.

a. glycation

b. glycosylation

c. phosphorylation

d. proteolysis

e. exonuclease digestion


66. In eukaryotic cells, proteins that contain covalently attached sugar residues are

translated

a. in the nucleus.

b. in the cytoplasm.

c. in mitochondria.

d. on the endoplasmic reticulum.

e. on the Golgi apparatus.


67. Mutations are

a. heritable changes in the sequence of DNA bases that produce an observable phenotype.

b. heritable changes in the sequence of DNA bases.

c. mistakes in the incorporation of amino acids into proteins.

d. heritable changes in the mRNA of an organism.


Textbook Reference: 12.6 What Are Mutations? p. 274

68. The type of mutation that stops translation of a protein is a(n)

a. missense mutation.

b. nonsense mutation.

c. frame-shift mutation.

d. aberration.



69. The type of mutation that is an insertion or a deletion of a single base is a(n)

a. missense mutation.

b. nonsense mutation.

c. frame-shift mutation.

d. aberration.



70. Sickle-cell disease is caused by a _______ mutation.

a. nonsense

b. missense

c. frame-shift

d. temperature sensitive

e. silent


71. Breaking and rejoining of chromosomes can lead to

a. deletions.

b. duplications.

c. inversions.

d. translocations.

e. All of the above


72. Damage to DNA can be caused by _______ absorbed by thymine in DNA, causing

interbase covalent bonds.

a. X-rays

b. cosmic radiation

c. ultraviolet radiation

d. smoke

e. cigarettes


73. The rates of DNA mutations are _______ in different organisms.

a. the same

b. constant

c. different

d. dependent on health

e. dependent on temperature


Fill in the Blank

1. The lethal toxin that is produced by the castor bean plant and that blocks protein

synthesis is _______.

Textbook Reference: 12.0 Toxic Avenger at the Ribosome, pp. 256–257

2. Biologists often look for organisms that are easy to grow in the laboratory and

demonstrate the phenomenon they wish to study. These organisms are called _______

organisms.


3. Certain agents, such as X-rays, that are known to cause mutations are referred to as

_______.


4. Prototrophs (“original eaters”) grow on minimal media, whereas _______ (“increased

eaters”) require specific additional nutrients.


5. The one-gene, one-enzyme hypothesis resulted from the work of ______.


6. The basic units of DNA and RNA molecules are the _______.


7. RNA differs from DNA in base composition in that it contains _______ instead of

thymine.


8. The strand of DNA that is transcribed into RNA is the _______ strand.


Produce RNA? p. 261

9. The synthesis of DNA from RNA is called _______.


Produce RNA? p. 261

10. The excess of codons (64) over amino acids (20) indicates that the genetic code is

_______.


Produce RNA? p. 264

11. The fact that some tRNA molecules do not have to pair exactly is called _______.


12. The portion of the tRNA molecule that complementary base-pairs with the mRNA is

called the _______.


13. A tRNA that has bonded to an amino acid is referred to as _______ tRNA.


14. Small ribosomal subunits will disperse into smaller components when placed in a

detergent solution. Upon removal of the detergent, the components will interact to create

new intact subunits by a process called _______.


15. An mRNA molecule with several ribosomes attached is called a(n) _______.


16. The part of a protein that determines whether translation will continue in the cytosol

or at the endoplasmic reticulum is the _______ sequence.


17. The addition of phosphate groups to polypeptide chains following translation is called

_______.


18. A mutation that causes a change in the nitrogenous base sequence of a DNA molecule

but no change in the amino acid sequence it codes for is called a(n) _______ mutation.


Diagram

1. Refer to the diagram below showing the process of gene expression in prokaryotes to

answer the question that follows.

The molecule responsible for carrying and delivering amino acids in the proper sequence

is/are

a. rRNA.

b. mRNA.

c. tRNA.

d. DNA.

e. DNA and mRNA.


STUDY GUIDE QUESTIONS

Knowledge and Synthesis Questions

1. Transcription in prokaryotic cells

a. occurs in the nucleus, whereas translation occurs in the cytoplasm.

b. is initiated at a start codon with the help of initiation factors and the small subunit of

the ribosome.

c. is initiated at a promoter and uses only one strand of DNA, the template strand, to

synthesize a complementary RNA strand.

d. is terminated at stop codons.


Produce RNA? p. 261

2. Which of the following about RNA polymerase is not true?

a. It synthesizes mRNA in a 5-to-3 direction reading the DNA strand 3-to-5.

b. It synthesizes mRNA in a 3-to-5 direction reading the DNA strand 5-to-3.

c. It binds at the promoter and unwinds the DNA.

d. It does not require a primer to initiate transcription.


Produce RNA? p. 262

3. Translation of messenger RNA into protein occurs

a. in a 3-to-5 direction and from N terminus to C terminus.

b. in a 5-to-3 direction and from N terminus to C terminus.

c. in a 3-to-5direction and from C terminus to N terminus.

d. in a 5-to-3 direction and from C terminus to N terminus.

Textbook Reference: 12.4 How Is RNA Translated into Proteins? pp. 269–270, Figure

12.12

4. If a codon were read two bases at a time instead of three bases at a time, how many

different possible amino acids could be specified?

a. 16

b. 64

c. 8

d. 32


Produce RNA? p. 264

5. Translate the following mRNA:

3-G A U G G U U U U A A A G U A- 5

a. NH2 met—lys—phe—leu—stop COOH

b. NH2 met—lys—phe—trp—stop COOH

c. NH2 asp—gly—phe—lys—val COOH

d. NH2 asp—gly—phe—lys—stop COOH


Produce RNA? p. 264

6. What would happen if a mutation occurred in DNA such that the second codon of the

resulting mRNA was changed from UGG to UAG?

a. Nothing. The ribosome would skip that codon and translation would continue.

b. Translation would continue, but the reading frame of the ribosome would be shifted.

c. Translation would stop at the second codon, and no functional protein would be made.

d. Translation would continue, but the second amino acid in the protein would be

different.

Textbook Reference: 12.6 What Are Mutations?

pp. 275–276

7. If the following synthetic RNA were added to a test tube containing all the components

necessary for protein translation to occur, what would the amino acid sequence be?

5-A U A U A U A U A U A U - 3

a. Polyphenylalanine

b. Isoleucine-tyrosine-isoleucine-tyrosine

c. Isoleucine-isoleucine-isoleucine-isoleucine

d. Tyrosine-tyrosine-tyrosine-tyrosine


Produce RNA? pp. 264–265

8. What part of the tRNA base-pairs with the codon in the mRNA?

a. The 3 end, where the amino acid is covalently attached

b. The 5 end

c. The anticodon

d. The promoter


9. Peptidyl transferase is an

a. enzyme found in the nucleus of the cell that assists in the transfer of mRNA to the

cytoplasm.

b. enzyme found in the large subunit of the ribosome that catalyzes the formation of the

peptide bond in the growing polypeptide.

c. RNA molecule that is catalytic.

d. Both b and c


10. Termination of translation requires

a. release factor, initiator tRNA, and ribosomes.

b. initiation factors, the small subunit of the ribosome, and mRNA.

c. elongation factors and charged tRNAs.

d. a stop codon positioned at the A site of the ribosome, peptidyl transferase, and release

factor.


11. Which of the following mutations would probably be the most deleterious?

a. A missense mutation in the second codon

b. A frame-shift mutation in the second codon

c. A nonsense mutation in the last codon

d. A silent mutation in the second codon

Textbook Reference: 12.6 What Are Mutations?

pp. 275–276

12. If the DNA encoding a nuclear signal sequence were placed in the gene for a

cytoplasmic protein, what would happen?

a. The protein would be directed to the lysosomes.

b. The protein would be directed to the nucleus.

c. The protein would be directed to the cytoplasm.

d. The protein would stay in the endoplasmic reticulum.


13. Auxotrophs are mutant strains that

a. can grow on a minimal medium.

b. require the addition of an essential nutrient to grow on a minimal medium.

c. behave like wild-type strains.

d. can only grow if arginine is added to the growth medium.


14. The central dogma of molecular biology states that _______ is transcribed into

_______, which is translated into _______.

a. genes; polypeptides; gene product

b. protein; DNA; RNA

c. DNA; mRNA; tRNA

d. DNA; RNA; protein

Textbook Reference: 12.2 How Does the Information Flow from Genes to Proteins? p.

260

15. A gene product can be a(n)

a. enzyme.

b. polypeptide.

c. RNA.

d. All of the above


16. The enzyme that catalyzes the synthesis of RNA is

a. DNA polymerase.

b. tRNA synthetase.

c. ribosomal RNA.

d. RNA polymerase.


Produce RNA? p. 262

Application Questions

1. What would be the effect of a deletion of the DNA encoding the targeting sequence for

that gene product? (Imagine that this protein was targeted to go to the mitochondria and

the signal sequence was removed as a result of this deletion.)

Textbook Reference: 12.5 What Happens to Polypeptides after Translation? pp. 272–274

2. What would happen if the tRNA synthetase for tryptophan actually added a

phenylalanine to the trp tRNAs instead of tryptophan?

Textbook Reference: 12.4 How Is RNA Translated into Proteins? pp. 267–268

3. Mutations can be very harmful to an organism, yet without them life as we know it

today would not exist. Explain.

Textbook Reference: 12.6 What Are Mutations? pp. 277–278

4. Suppose that two different mutant strains of a bacterium are unable to grow on a

minimal medium without the addition of the amino acid lysine. Explain how this

phenotype might be caused by different mutations in each strain, perhaps on the same

gene and perhaps in two different genes.


5. When fed the same biochemical intermediate, two auxotrophic mutants that had been

isolated were able to grow. According to the experiments of Beadle and Tatum, the

mutations in each of these auxotrophs should be in the same gene, because they were

blocked at the same step in a biochemical pathway. Yet, these two auxotrophs had

mutations that mapped in different genes. How do you explain this?


ONLINE QUIZ QUESTIONS

1. Which of the following about the genetic code is true?

a. It is degenerate.

b. It changes a great deal over short periods of time.

c. It is ambiguous.

d. It has 64 codons that code for amino acids.

e. It is completely different for prokaryotes and eukaryotes.


Produce RNA? p. 263

2. A Neurospora mutant cannot grow unless the amino acid, leucine, is added to its

growth medium. This strain is

a. dependent on leucine for energy.

b. mutated in genes coding for the synthesis of all 20 amino acids.

c. inhibited by leucine.

d. wild-type for the synthesis of all amino acids except for leucine.

e. mutated for the synthesis of all amino acids except for leucine.


3. Which of the following is not a phase that occurs during translation?

a. Termination

b. Initiation

c. Conjugation

d. Elongation

e. All of these phases occur in translation.


4. RNA polymerase

a. adds nucleotides to the 3’ hydroxyl group of the last nucleotide.

b. functions similarly to DNA polymerase.

c. adds nucleotides to the 5’ hydroxyl group of the last nucleotide.

d. Both a and b

e. Both b and c


Produce RNA? p. 262

5. An initiator methionine–tRNA complex is positioned at the AUG start codon in order

to start elongation in protein synthesis.

a. True

b. False


6. A mutation that occurs when a mutagen causes a permanent change in DNA is

a. inversion.

b. deletion.

c. duplication.

d. induced mutation.

e. translocation.


7. Triplet codons

a. can have amino acids that are represented by more than one codon and are not specific.

b. are tRNA codons.

c. are not relatively universal and change frequently over time.

d. help bind the promoter and unwind the DNA strands.

e. can be stop codons or start codons.


Produce RNA? p. 263

8. Which of the following was hypothesized to have traveled through the nucleus to the

cytoplasm, where it served as a template for the synthesis of proteins?

a. tRNA

b. mRNA

c. RNA

d. DNA

e. The central dogma


and Figure 12.2

9. The main difference between DNA and RNA is that

a. RNA lacks pyrimidine bases.

b. DNA lacks purine bases.

c. DNA lacks a 2’ hydroxyl group.

d. RNA lacks a 2’ hydroxyl group.

e. Both a and c


10. Which of the following single base substitutions in the sense strand of DNA would

cause a change in phenotype?

a. CCT to CCC

b. GAG to TAG

c. ATG to ATT

d. CTG to CTT

e. CAA to CAG


Produce RNA? p. 263

11. Which of the following is a stop codon?

a. UAA

b. UGC

c. UAC

d. UUA

e. UGG


Produce RNA? p. 263 and Figure 12.6

12. Which of the following is a function of tRNA?

a. It is the main constituent of ribosomes.

b. It transports amino acids.

c. It acts as a template for translation.

d. It recognizes four bases on the mRNA.

e. tRNAs all carry the same anticodon.


13. Put the following events about protein synthesis in chronological order.

(1) After peptide linkage, the empty P site tRNA shifts to an exit site on the ribosome.

(2) The ribosome releases the empty tRNA as it translocates the length of one codon.

(3) The next tRNA binds the A site.

(4) A tRNA is positioned at the AUG start codon.

(5) The amino acid at the P site is transferred to the amino acid attached to the tRNA at

the A site.

(6) The A site is now free for the next incoming tRNA.

a. 4; 1; 5; 3; 6; 2

b. 4; 6; 1; 2; 3; 5

c. 4; 1; 5; 2; 3; 6

d. 4; 3; 5; 1; 2; 6

e. 4; 2; 5; 1; 3; 6


14. Which of the following is the correct order in which a charged tRNA travels?

a. E site; P site; A site; T site

b. P site; E site; A site; T site

c. T site; A site; P site; E site

d. A site; T site; E site; P site

e. E site; P site; T site; A site


15. Anticodons are made of mRNA.

a. True

b. False


16. The termination of transcription is signaled by

a. the stop codon.

b. a sequence of bases.

c. a protein bound to DNA.

d. RNA polymerase running out of template.

e. lack of deoxyribonucleoside triphosphates.


Produce RNA? p. 262

17. Which of the following is not a characteristic of RNA?

a. RNA contains uracil as a base.

b. The sugar molecule in RNA is ribose.

c. RNA can base-pair with DNA.

d. RNA consists of a single polynucleotide strand.

e. RNA contains more bases than DNA.


18. Beadle and Tatum originally proposed the one-gene, one-enzyme hypothesis. Today,

this hypothesis could be restated in which of the following ways?

a. Each gene contains all the information to make one lipid or one carbohydrate.

b. Each protein is the result of the activity of one enzyme.

c. One DNA molecule contains the information to make one enzyme.

d. A gene is really an enzyme that catalyzes the production of a single protein.

e. A given sequence of DNA nucleotides contains the information to make one enzyme.


19. When examining the genetic code, it is apparent that

a. there can be more than one amino acid for a particular codon.

b. AUG is a terminating codon.

c. there can be more than one codon for a particular amino acid.

d. the code is ambiguous in that the same codon can code for two or more amino acids.

e. there are 44 stop codons because there are only 20 amino acids.

Answer c


Produce RNA? p. 263

20. A mutation that arises from a single base change in a codon _______ the amino acid

coded for.

a. will change

b. will not change

c. may or may not change

d. will be repaired so that it will have no effect on



TEXTBOOK END-OF-CHAPTER QUESTIONS

1. Which of the following is not a difference between RNA and DNA?

a. RNA has uracil; DNA has thymine.

b. RNA has ribose; DNA has deoxyribose.

c. RNA has five bases; DNA has four.

d. RNA is a single polynucleotide strand; DNA is a double strand.

e. RNA is relatively smaller than human chromosomal DNA.

2. Normally, Neurospora can synthesize all 20 amino acids. A certain strain of this mold

cannot grow in minimal nutritional medium, but grows only when the amino acid leucine

is added to the medium. This strain

a. is dependent on leucine for energy.

b. has a mutation affecting the biochemical pathway leading

to the synthesis of proteins.

c. has a mutation affecting the biochemical pathway leading

to the synthesis of all 20 amino acids.

d.has a mutation affecting the biochemical pathway leading

to the synthesis of leucine.

e. has a mutation affecting the biochemical pathways leading to the syntheses of 19 of the

20 amino acids.

3. An mRNA has the sequence 5'-AUGAAAUCCUAG-3'. What is the template DNA

strand for this sequence?

a. 5'-TACTTTAGGATC-3'

b. 5'-ATGAAATCCTAG-3'

c. 5'-GATCCTAAAGTA-3'

d. 5'-TACAAATCCTAG-3'

e. 5'-CTAGGATTTCAT-3'

4. The adapters that allow translation of the four-letter nucleic acid language into the 20-

letter protein language are called

a. aminoacyl-tRNA synthetases.

b. transfer RNAs.

c. ribosomal RNAs.

d. messenger RNAs.

e. ribosomes.

5. At a certain location in a gene, the non-template strand of DNA has the sequence GAA.

A mutation alters the triplet to GAG. This type of mutation is called

a. silent.

b. missense.

c. nonsense.

d. frame-shift.

e. translocation.

6. Transcription

a. produces only mRNA.

b. requires ribosomes.

c. requires tRNAs.

d. produces RNA growing from the 5' end to the 3' end.

e. takes place only in eukaryotes.

7. Which statement about translation is not true?

a. It is RNA-directed polypeptide synthesis.

b. An mRNA molecule can be translated by only one ribosome at a time.

c. The same genetic code operates in almost all organisms and organelles.

d. Any ribosome can be used in the translation of any mRNA.

e. There are both start and stop codons.

8. Which statement about RNA is not true?

a. Transfer RNA functions in translation.

b. Ribosomal RNA functions in translation.

c. RNAs are produced by transcription.

d. Messenger RNAs are produced on ribosomes.

e. DNA codes for mRNA, tRNA, and rRNA.

9. The genetic code

a. is different for prokaryotes and eukaryotes.

b. has changed during the course of recent evolution.

c. has 64 codons that code for amino acids.

d. has more than one codon for many amino acids

e. is ambiguous.

10. A mutation that results in the codon UAG where there had been UGG is

a. a nonsense mutation.

b. a missense mutation.

c. a frame-shift mutation.

d. a large-scale mutation.

e. unlikely to have a significant effect.

ANSWERS

TEST FILE

Multiple Choice

1. b

2. a

3. a

4. e

5. a

6. b

7. d

8. d

9. e

10. a

11. d

12. b

13. a

14. c

15. c

16. b

17. e

18. a

19. b

20. a

21. c

22. e

23. a

24. d

25. b

26. d

27. c

28. b

29. c

30. b

31. c

32. a

33. b

34. b

35. b

36. b

37. a

38. e

39. e

40. a

41. c

42. d

43. c

44. e

45. d

46. a

47. d

48. d

49. b

50. e

51. b

52. e

53. d

54. d

55. b

56. e

57. d

58. b

59. a

60. a

61. c

62. a

63. d

64. b

65. d

66. d

67. b

68. b

69. c

70. b

71. e

72. c

73. c

Fill in the Blank

1. ricin

2. model

3. mutagens

4. auxotrophs

5. Beadle and Tatum

6. nucleotides

7. uracil

8. template

9. reverse transcription

10. redundant

11. wobble

12. anticodon

13. charged

14. self-assembly

15. polysome

16. signal

17. phosphorylation

18. silent

Diagram

1. c

STUDY GUIDE

Knowledge and Synthesis

1. c. Answer a describes transcription and translation in eukaryotic cells; answers b and d

describe translation.

2. b. RNA polymerase binds at a promoter, unwinds the DNA, synthesizes mRNA in a 5-

to-3 (not 3-to-5) direction, and does not require a primer to synthesize the RNA.

3. b. Translation of messenger RNA occurs 5 to 3, and the polypeptide is synthesized

from N terminus to C terminus.

4. a. Four possible bases read two at a time gives 42, or 16, different codons.

5. b. See the codon table, Figure 12.6. Recall that translation occurs in the 5-to-3

direction.

6. c. UAG is a stop codon, so translation would terminate at that site.

7. b. See the codon table, Figure 12.6.

8. c. Neither the 3 end nor the 5 end of the tRNA is part of the anticodon. The promoter

is a DNA sequence, to which RNA polymerase binds to initiate transcription.

9. d. Peptidyl transferase is the enzyme that catalyzes the formation of the peptide bond,

and it is located in the large subunit of the ribosome. Its catalytic activity is due to

ribosomal RNA found in the large subunit of the ribosome.

10. d. Termination of translation requires a stop codon to be positioned in the A site of

the ribosome, and peptidyl transferase and release factor. Peptidyl transferase adds water

across the last amino acid attached to the tRNA in the P site, creating the C terminus.

11. b. The mutation that is potentially the most dangerous is the frame-shift in the second

codon. All of the other codons would be out of register and no functional protein could be

made. A missense mutation in the second codon could be disastrous or minimal,

depending on how crucial that second amino acid was to the folding and functioning of

the protein. A nonsense mutation at the end of the coding sequence would have less effect

on protein function because almost every amino acid in the protein would have been

correctly synthesized. Again, this would depend on how important that last codon was to

the proper folding and functioning of the protein. A silent mutation would have no effect

on protein function because the amino acid inserted at that codon would be the same.

12. b. The nuclear sequence would direct this protein to be delivered to the nucleus.

13. b. Answer d is true only for arginine auxotrophs.

14. d. Genes are not transcribed into polypeptides, protein is not transcribed into DNA,

and messenger RNAs are not translated into tRNAs.

15. d. Gene products can be RNAs (such as rRNA and tRNA) as well as enzymes and

other polypeptides. Messenger RNA is translated into a gene product, protein.

16. d. DNA polymerase catalyzes the synthesis of DNA, tRNA synthetase covalently

attaches amino acids to tRNAs, and ribosomal RNA (in the large subunit) catalyzes the

formation of the peptide bond during translation.

Application

1. Because the protein lacked its targeting sequence, it would no longer be moved to the

mitochondria and would remain in the cytoplasm after it had been translated.

2. If the tRNA synthetase for tryptophan added phenylalanine to the trp tRNAs, everytime

a tryptophan codon was read by these trp tRNAs, phenylalanine would be added to the

polypeptide. This would create proteins that were nonfunctional, and the cell would die.

3. Mutations very often have damaging effects on a gene, rendering that gene product

nonfunctional. Some mutations actually create gene products that are better for the cell or

organism and may increase its ability to survive. Mutations over the course of

evolutionary time have created new organisms that could survive in different

environments or compete more effectively for limited resources. Without mutations

evolution does not occur.

4. The mutations in these two strains of bacteria apparently interfere with lysine synthesis.

The mutations might both be in the same gene coding for an enzyme necessary for lysine

synthesis, but one could be a nonsense mutation in the fifth codon and the other a frame-

shift mutation in the twenty-third, for example (the number of mutations that can disable

a gene is enormous). If lysine synthesis in this bacterium requires more than one enzyme

(as is likely), the two mutations could be in different genes coding for different enzymes.

In this case, the phenotypes would not be strictly identical; it should be possible to

distinguish the two by trying to grow them on minimal media to which different

intermediates in the synthesis of lysine have been added (see Figure 12.1).

5. These two genes must encode different polypeptides that are both subunits for the same

enzyme in this biochemical pathway.

ONLINE QUIZ

1. a

2. d

3. c

4. d

5. a

6. d

7. e

8. b

9. c

10. c

11. a

12. b

13. d

14. c

15. b

16. b

17. e

18. e

19. c

20. c

TEXTBOOK END-OF-CHAPTER

1. c

2. d

3. e

4. b

5. a

6. d

7. b

8. d

9. d

10. a

Ch12 test file

Health & Medicine

Transcript of Ch12 test file