E) phosphate group E) x-ray crystallography B) RNA A) transformation A) Hershey and Chase (1952) B) Histones A) Nucleic acids B) euchromatin

Transcription

1 1. Rosalind Franklin s pictures of the DNA double helix were taken using the technique known as A) bright field microscopy B) diffraction C) fluorescence D) transmission electron microscopy E) x-ray crystallography 2. Frederick Griffith experimented with two strains of pneumonia, an S (smooth) and an R (rough) strain. When injected into test mice, the S strain was able to kill its host while the R strain was not. However, when the S strain were killed by heat, and their remains were added to R strain bacteria they were able to kill its host. This phenomenon can best be described by A) transformation B) transduction C) mutation D) induction E) replication 3. Which of the following scientists determined that DNA is the hereditary material in viruses? A) Hershey and Chase (1952) B) Griffith (1928) C) Watson and Crick (1953) D) Morgan (1950's) E) Meselson and Stahl (1950's) 4. Which of the following proteins are responsible for the first level of packing in eukaryotic chromatin? A) Proteasomes B) Histones C) Episomes D) Prions E) Tubulin 5. DNA is the polymer for which class of compounds? A) Nucleic acids B) RNA C) Proteins D) Amino acids E) Genes 6. Chromosomes that are completely condensed contain all of the following structures EXCEPT A) histones B) euchromatin C) helices D) heterochromatin E) nucleosomes 7. The 5 end of a DNA nucleotide can be identified by the location of A) carbon B) hydrogen bonds C) nitrogenous bases D) oxygen E) phosphate group 8. A single strand containing phosphate, ribose, and the bases adenine, guanine, uracil and cytosine is called A) DNA B) RNA C) enzyme D) sugar E) base

2 Base your answers to questions 9 through 11 on the diagram below. 9. These run antiparallel to one another. A) A and E B) A and D C) A and B D) C and D E) D and E 10. Hydrogen bonds that join bases of the helix together are represented by letter A) A B) B C) C D) D E) E 11. A phosphate group is represented by letter A) A B) B C) C D) D E) E 12. DNA has all of the following characteristics EXCEPT A) the molecule is single stranded B) contains sugar phosphate backbones C) nitrogenous bases are linked by hydrogen bonds D) one end has a 5' phosphate group and the other has a 3' hydroxyl group E) the molecule is antiparallel 13. One of the strands of DNA in a double helix has the base sequence ATGATTC. The base sequence of the complementary strand of DNA is A) TACTAAG B) TUCTUUG C) GACGAAT D) CAGCAAG E) UACUAAG 14. Which of the following does NOT describe RNA? A) Is made up of a nitrogenous base, a five carbon sugar, and a phosphate group B) May contain any of the these phosphate groups - adenine, guanine, uracil, cytosine C) Single-stranded D) RNA is transcribed in the cytoplasm of a cell E) Transcribed from a DNA template by RNA polymerase

3 15. A eukaryotic cell lacking helicase during DNA replication would A) be incapable of proofreading the newly synthesized strand B) be unable to terminate elongation C) be incapable of unwinding the DNA helix D) catalyze the DNA strand at incorrect locations E) not seal the Okazaki fragments on the lagging strand 16. During DNA replication, all of the following must occur before the completion of a new strand EXCEPT A) separation of the parental DNA strands by the DNA helicase B) primase joins RNA nucleotides to make a primer C) telomerase terminates replication at the end of the synthesized strand D) DNA polymerase replaces RNA nucleotides with DNA nucleotides E) telomeres are added to the end of the synthesized strand 17. During DNA replication, the leading strand is easily distinguishable from the lagging strand because A) the leading strand is synthesized 3' to 5' B) the lagging strand is synthesized in separate pieces called Okazaki fragments C) helicases only attach to the leading strand D) the lagging strand is synthesized 5' to 3' E) DNA ligase is attached to the leading strand 18. Although eukaryotic cells contain over a thousand times more DNA than is found in a prokaryotic cell, it only takes a eukaryotic cell a few hours to copy all of its genetic material because A) eukaryotic DNA polymerases delete unnecessary material as it is replicating B) eukaryotic cells follow the semiconservative model for DNA replication C) prokaryotic cells have more than four nucleotide bases D) eukaryotic cells have more than one replication site along its chain of DNA E) eukaryotic cells have shorter segments of DNA 19. DNA replication is a semiconservative process because in the double helix A) there are two strands, one from the template, and a new complementary strand B) the template molecule remains mostly intact C) there are four strands, each containing a mixture of old and new DNA D) there is only one origin of replication E) DNA polymerase can only add nucleotides to the 3' end of a molecule thereby limiting mutations 20. Which of the following sequences expresses the correct order of enzyme function in DNA replication? A) helicase primase DNA polymerase ligase B) helicase primase ligase DNA polymerase C) helicase primase ligase hydrolase D) primase helicase ligase DNA polymerase E) primase helicase DNA polymerase ligase 21. Okazaki fragments are joined by A) DNA helicase B) DNA ligase C) DNA polymerase D) DNA primase E) topoisomerase 22. Okazaki fragments are formed on A) DNA lagging strand B) DNA leading strand C) mrna strand D) trna strand E) rrna 23. In DNA synthesis, DNA is A) read 3 to 5 and made 3 to 5 B) read 3 to 5 and made 5 to 3 C) read 5 to 3 and made 3 to 5 D) read 5 to 3 and made 5 to 3 E) read 5 to 5 and made 3 to 3

4 24. Following the elongation phase of transcription, what happens to the template DNA strands? A) They are removed from the nucleus to prevent double replication. B) They are rewound into a double helix. C) They are modified and released from the nucleus. D) They are capped with a poly (A) tail to inhibit degradation. E) They are spliced and packaged into ribosomes. 25. Before a molecule of mrna can leave the nucleus it must A) remove the noncoding regions called exons B) excise the introns and splice the exons together C) splice together the 5'cap and the polya tail D) excise the exons and attach the polya tail E) be translated by the RNA polymerase 26. The 5' cap placed on the end of each pre-mrna molecule functions to A) promote the attachment of RNA polymerase B) provide a marker site for spliceosomes to begin the removal of introns C) signal attachment for polyribosomal clusters D) provide a signal for the attachment of genes E) protect the mrna from degradation and provide a signal for ribosome attachment 27. Which of the following statements is true about DNA polymerase and RNA polymerase? A) Both can only add nucleotides to the 3' end of the growing polymer. B) Both are responsible for unwinding the DNA helix and adding nucleotides. C) RNA molecules elongate in the 3' to 5' direction while DNA elongates 5' to 3'. D) DNA polymerase is only used during transcription and RNA polymerase is only used during translation. E) Both are used during translation. 28. Which of the following is responsible for prying the DNA helix apart in order to transcribe the mrna? A) helicase B) RNA polymerase C) promoter D) DNA polymerase E) spliceosome 29. In prokaryotic cells, the transcription initiation complex binds to A) a primer B) the termination sequence C) a promoter sequence on the DNA molecule D) the codon E) an mrna molecule 30. If a segment of DNA contains the sequence 5'-GAT TTA ATG-3', the resulting RNA must be A) 3'-CAU UAA AUC-5' B) 3'-CUA AAU UAC-5' C) 3'-CTA TTA TAC-5' D) 3'-CAT TAA ATC-5' E) 3'-GAT TTA ATU-3' 31. Retroviruses are used by genetic engineers to transform mrna into DNA because mrna does not include A) exons B) GTP cap C) non-coding regions D) nucleotide tails E) stop codons 32. Mature mrna is different from immature mrna in that A) mature mrna is formed within the nucleus B) mature mrna lacks exons C) mature mrna has a poly A tail D) mature mrna lacks a double helix conformation E) mature mrna contains uracil 33. Spliceosomes and small nuclear ribonucleoproteins are involved in A) formation of mature mrna B) formation of mature trna C) DNA splicing D) lysis of GTP cap E) recognition of initial codon

5 34. You conduct an experiment to determine which strand of DNA serves as the template for mrna synthesis. First, you obtain DNA and transcribe mrna from it. The DNA strands are then separated and analyzed. The below data shows the composition of each strand. Which strand serves as the coding strand, which serves as the template for the mrna transcription? A) Strand 1 B) Strand 2 C) Neither strand D) Both strands E) mrna strand 35. The triplet of nucleotides of mrna that corresponds to another unit of nucleotides in trna is the A) codon B) anticodon C) peripheral D) cistron E) anticistron 36. The synthesis of DNA from RNA requires which enzyme? A) Reverse transcriptase B) RNA polymerase C) Reverstase D) DNA polymerase I E) RNA polymerase 37. What would occur if an mrna molecule did not have polyribosomes? A) Polypeptides would form at a slower pace. B) Amino acids would not elongate. C) The trna in the A site would not translocate to the P site. D) The small ribosomal unit would not bind to the large ribosomal subunit. E) The ribosomal subunits would not be recycled. 38. What would happen if a polypeptide is NOT marked by a signal peptide? A) It would end up attached to the plasma membrane. B) It could not move into the endoplasmic reticulum. C) It would keep elongating without termination. D) It would be degraded by the signal-recognition particle. E) It would never leave the nucleus. 39. Why are polyribosomes important to both eukaryotic and prokaryotic cells? A) They are an important component of the translation initiation complex. B) They unwind the DNA helix. C) They are necessary for the removal of the introns from the pre-mrna molecule. D) They ensure the correct binding between trna and amino acids. E) They can make many copies of a polypeptide very quickly. 40. Which of the following is important during the translocation of trna from the A site to the P site? A) The maintenance of hydrogen bonds between the anticodon and mrna codon. B) The mrna moving in the 3' to 5' direction. C) The ribosome bypassing the intron regions on the mrna strand. D) The release factor must bind in order to move the trna molecules. E) The small ribosomal subunit must dissociate from the mrna strand. 41. The large and small subunits of a eukaryote's ribosome are made in the A) cytoplasm B) nucleolus C) rough endoplasmic reticulum D) mitochondria E) golgi apparatus

6 42. Which of the following is true about trna in prokaryotic and eukaryotic cells? A) The trna molecule cannot leave the nucleus. B) Each trna can attach to any one of the 20 amino acids. C) The trna molecule can be used repeatedly. D) The anticodon of the trna consists of four nucleotide bases. E) Each trna molecule can be used once. 43. A trna molecule transfers amino acids from a pool located in which of the following locations? A) Plasma membrane B) Endoplasmic reticulum C) Golgi apparatus D) Nucleus E) Cytoplasm 44. Base your answer to the following question on the chart below. If a polypeptide chain has the amino acid sequence, Leu-Arg-Lys, what would be the corresponding anticodons found on the trna? A) CCA CGA TTT B) CCA CGA AAA C) GGU GCU UUU D) GGU GCU AAA E) GGT CCA TTT

7 45. What event occurs when a ribosome reaches a termination codon on mrna? A) The A site of the ribosome accepts another trna called the terminator. B) The polypeptide chain releases from the P site of the ribosome. C) The A site of the ribosome accepts a protein called a release factor. D) The two ribosomal subunits dissociate and release the polypeptide chain. E) The ribosome undergoes a conformation change. 46. During translation, the initiation complex is composed of A) an RNA polymerase, a DNA molecule, and accessory proteins B) an mrna, a trna molecule, and two ribosomal subunits C) a DNA polymerase, an mrna molecule, and a polypeptide chain D) a trna molecule, an amino acid, and an anticodon E) an mrna, an rrna molecule, and a small ribosomal subunit 47. The anticodon region can be found A) within a trna molecule B) on the polypeptide chain C) within an mrna molecule D) on the large subunit of the ribosome E) attached to the end of an amino acid

8 Base your answers to questions 48 through 50 on the image below. 48. Identify the structure indicated by the letter C A) polypeptide B) DNA C) codon D) mrna E) nuclear envelope 49. Identify the structure indicated by letter B A) DNA B) mrna C) trna D) polypeptide chain E) nucleotide chain 50. A triplet code is responsible for A) attaching amino acids to DNA B) encoding the instructions for the polypeptide chain C) placing the correct protein on the mrna strand D) transcribing the DNA strand from its template E) synthesizing mrna from a complementary protein strand 51. Essential amino acids are those A) only acquired from external food sources B) immediately required for synthesis of a specific protein C) necessary for DNA synthesis D) packaged by the Golgi body for secretion E) regularly produced by the cells

9 Base your answers to questions 52 through 55 on the following diagram 52. The sequence depicted above binds to the opposite sequence on another molecule by A) disulfide bonds B) hydrogen bonds C) ionic bonds D) phosphodiester linkages E) van der Waals forces 53. The above picture depicts A) DNA B) mrna C) rrna D) trna E) none of the above 54. The corresponding nucleotide sequence for the one depicted above is A) TAA B) UAA C) ATT D) AUC E) CAA 55. The above picture is composed of A) anticodon B) codon C) cistron D) exon E) intron 56. During translation, mrna A) binds to the A site B) binds to the P site C) moves from A to P site D) moves from P to A site E) does not occur 57. How many amino acids could be coded for using the mrna sequence 5'GUCGACGUC3'? A) 1 B) 2 C) 3 D) 6 E) Which of the following best represents the expression of genes? A) DNA RNA Protein B) DNA Protein RNA C) RNA Protein DNA D) RNA DNA Protein E) Protein RNA DNA 59. A protein molecule is composed of 45 amino acids. How many nucleotides long was the DNA sequence that coded for the amino acids? A) 3 B) 15 C) 45 D) 90 E) The end products of translation are A) DNA B) RNA C) lipids D) amino acids E) polypeptides 61. All of the following are steps involved in protein synthesis EXCEPT A) transcription B) initiation C) replication D) elongation E) translation 62. Which of the following occurs during the alteration after translation? A) Excision of introns B) Excision of exons C) Addition of a poly(a) tail D) Formation of peptide bonds E) Proteins form a quaternary structure 63. Fifteen nucleotides code for a protein which contains how many amino acids? A) 3 B) 5 C) 15 D) 30 E) How many DNA nucleotides are needed to code for a subunit which is 120 amino acids long? A) 40 B) 60 C) 120 D) 240 E) 360

10 65. Which of the following statements about translation is INCORRECT? A) All three types of RNA (messenger, transfer, and ribosomal) are involved in translation. B) A strand of mrna dictates the amino acids that will be incorporated into protein. C) rrnas carry the amino acids to the mrna strand. D) The mrna has codons which form base pairs with the anticodons on the trna. E) Protein synthesis occus on ribosomes. 66. The cytosolic process whereby a strand of messenger RNA dictates the amino acids that will be incorporated into protein is called A) translocation B) transpiration C) transfusion D) translation E) transcription 67. Hershey and Chase conducted an experiment using phage. What did their experiment consist of? What conclusion did they reach regarding the composition of DNA? Base your answers to questions 68 through 70 on the choices below. Match the scientist to their contribution to the study of biology. (A) Alfred Hershey & Martha Chase (B) Rosalind Franklin (C) George Beadle & Edward Tatum (D) Frederick Griffith (E) Barbara McClintock 68. Based the one gene-one enzyme hypothesis on the study of nutritional mutants of Neurospora crassa, a red bread mold 69. Discovered that molecules from the dead S strain of the bacterium Streptococcus pneumoniae had genetically transformed some of the living R strain bacteria into S strain bacteria 70. Discovered that DNA is the genetic material of a bacteriophage known as T2

11 71. Base your answer to the following question on the diagrams of organic molecules below. DNA is a polymer of these molecules. 72. Describe the major steps of DNA replication in an animal cell. Base your answers to questions 73 through 75 on the choices below. (A) Helicase (B) Polymerase (C) Ligase (D) Topoisomerase (E) Primase 73. Brings together the Okazaki fragments 74. Adds nucleotides alongside the leading strand 77. Base your answer to the following question on the choices below. (A) Transformation (B) Translocation (C) Duplication (D) Conjugation (E) Translation Process in which a protein is synthesized at a ribosome 75. Cuts and rejoins the helix 76. Proteins are polypeptides formed from messenger RNA. In a unified response, discuss the three steps of translation. Include in your response a description of the three types of RNA and the location of the steps.

12 Answer Key Molecular Genetics Practice 1. E 2. A 3. A 4. B 5. A 6. B 7. E 8. B 9. C 10. E 11. C 12. A 13. A 14. D 15. C 16. C 17. B 18. D 19. A 20. A 21. B 22. A 23. B 24. B 25. B 26. E 27. A 28. B 29. C 30. B 31. C 32. C 33. A 34. B 35. A 36. A 37. A 38. B 39. E 40. A 41. B 42. C 43. E 44. C 45. C 46. B 47. A 48. D 49. D 50. B 51. A 52. B 53. D 54. A 55. A 56. C 57. C 58. A 59. E 60. E 61. C 62. E 63. B 64. E 65. C 66. D 67. (essay) 68. C 69. D 70. A 71. C 72. (essay) 73. C 74. B 75. D 76. (essay) 77. E

13 Answer Key Molecular Genetics Practice 67. Hershey and Chase used bacteriophages to show DNA is the genetic material of the cell rather than protein. In two separate experiments, they labeled one set of phage with radioactive sulfur (which labels protein) and the other phage with radioactive phosphorous (which labels the phage DNA). They infected E. coli cells with these phage and then agitated the mixture to dissociate phage from the bacterial surface. After centrifugation, levels of each isotope were measured in both the supernatant and the pellet. Sulfur was only detected in the supernatant and not in the pellet while phosphorous was detected in the cell and not in the supernatant. By showing that the phage inserts its genome into the host and subsequently causes changes to the cell, Hershey and Chase proved successfully that DNA is linked to heredity. 72. The replication of DNA molecules begin at special sites called origins of replication. DNA replication 'bubbles' proceed in both directions from each origin and eventually fuse to synthesize the daughter strands of DNA. Helicases unwind the parental double helix. Single-strand binding proteins stabilize the unwound parental DNA. Base pairing (Adenine pairs with Thymine, Cytosine pairs with Guanine) enables existing DNA strands to serve as templates for new complementary strands. DNA polymerase synthesizes the leading strand in the 5' ->3' direction. The lagging strand is synthesized on a discontinuous basis. Primase synthesizes a short RNA primer, which is extended by DNA polymerase to form an Okazaki fragment. After RNA primer is replaced by DNA via DNA polymerase, DNA ligase joins the Okazaki fragment to the growing strand. DNA replication is a semi-conservative process in that the replication of one DNA molecule yields two hybrid molecules, each composed of one parental strand and one newly-synthesized strand. 76. The three steps of translation are initiation, elongation, and termination. During initiation, a ribosomal subunit binds to a strand of messenger RNA (mrna). mrna, contains the nucleotide sequence produced from the transcription of DNA. An initiator transfer RNA, trna, with the anticodon UAC, carries the amino acid methionine. This anticodon pairs with the AUG start codon on the mrna. trna is a type of RNA that carries amino acids to the ribosomes for the production of polypeptides. The large ribosomal subunit then joins the smaller subunit, forming a complex. The initiator trna occupies the P site of the complex. The second trna and mrna move from the A site to the D site. The A site is empty, ready to accept the next trna carrying the correct amino acid. This process uses GTP as an energy source. The next step is the elongation step. A trna bound to an amino acid pairs with the codon in the A site. A peptide bond forms between the two amino acids through a catalyzed reaction once the bond between the trna and amino acid in the P site is broken. The trna in the A site, with the growing polypeptide chain, moves into the P site. The trna that previously occupied the P site moves to the E site and then exits the ribosome subunit complex. Elongation factors help in the formation of the polypeptide. The final step in polypeptide production is the termination of translation. When the ribosome recognizes a stop codon on the mrna, no trna is able to pair with the mrna sequence. A releasing factor moves into the A site of the ribosome. This hydrolyzes the bond between the last trna and amino acid, creating a free polypeptide. The ribosome is then able to dissociate.