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Chapter 7 Homework 1. Bacterial conjugation is often referred to as bacterial sex. Why is this term inaccurate? Bacteria are neither male nor female. Conjugation does not result in the formation of new offspring. It does not require two cells to occur. Sex is a phenomenon only seen in animals.

2. What must occur for bacterial conjugation to take place? The cells must transfer RNA. Each cell must contain a plasmid. The cells must come into contact with each other. One of the cells must be E. coli.

3. Which statement about conjugation is false? E. coli is the model for bacterial conjugation. After conjugation, each cell involved has a copy of the shared DNA. Conjugation is a process of bacterial reproduction. 4. Based on the animation, what is transferred during bacterial conjugation? A bacterial plasmid RNA A conjugation pilus A bacterial chromosome 5. What is unique about transduction compared to normal bacteriophage infection? The bacteriophage does not erupt from an infected cell during transduction. The bacteriophage takes fragments of the cell with it during transduction.

Chapter 7 Homework

Transduction transfers DNA from the chromosome of one cell to another.

6. How is generalized transduction different from specialized transduction? Generalized transduction is initiated during lytic cycle of a virulent bacteriophage; specialized transduction is initiated during the lysogenic cycle of a temperate bacteriophage. Generalized transduction is initiated by a lysogenic bacteriophage; specialized transduction is initiated by a lytic phage. Only one specific host gene is transferred in both specialized transduction and generalized transduction. Specialized transduction uses animal viruses instead of bacteriophage. 7. A transducing phage cannot infect new host cells. is a lysogenic bacteriophage. has a viral coat made of host proteins. contains fragments of the host chromosome instead of the viral genome. 8. When a transducing phage interacts with a new host cell, the new host cell will be lysed. it will cause the new cell to produce more transducing phage. the DNA from the previous host can recombine with the new host chromosome. 9. Competent cells are cells that have the ability to produce capsules. are also considered "rough-strain" based on colony phenotype. can take up DNA from their surrounding environment and integrate it into their own chromosomes by recombination. are killed by heat.

Chapter 7 Homework

10. Mice that are injected with only the R strain of Streptococcus pneumoniae stay healthy, because their immune systems can kill this strain easily. become sick for prolonged periods of time. are killed, because R strain cells are deadly. 11. What characteristic of the S strain allows it to evade the immune system of the mice? The cells have a capsule. They are naturally competent. They are genetically engineered to be resistant to killing. They are resistant to heat. 12. What most likely explains the recovery of live S strain cells from a mouse injected with heatkilled S strain mixed with live R strain cells? The R strain cells picked up the capsules from the S strain cells. The S strain was revived by the presence of the host’s immune system. The S strain fused with the R strain, making it resistant. The R strain picked up the S strain DNA, enabling it to produce a capsule. 13. Which finding is most surprising from Griffith’s experiments? S strains are able to escape phagocytosis. R strain cells fail to produce a capsule. S strain cells are isolated from the blood of mice infected with heat-killed S strains and live R strains. S strain cells kill the mice.

Chapter 7 Homework

14. A recombinant cell is the result of a cell dividing. is a cell that receives DNA from an outside source and incorporates it into its own. donates DNA into a new cell.

15. What is the hallmark of all horizontal gene transfers? Transfer of DNA between organisms of the same generation Transfer of DNA using a virus Transfer of DNA from parent to offspring The use of plasmids

16. Which of the following is an example of horizontal gene transfer in bacteria? Transformation Conjugation and transformation Transduction Conjugation Transduction, conjugation, and transformation 17. How does an F+ cell differ from an Hfr cell? Hfr strains have the F plasmid integrated into the chromosome. F+ cells have no plasmids. Hfr cells cannot perform conjugation. Hfr strains can no longer reproduce.

Chapter 7 Homework

18. Why does conjugation between an Hfr strain and an F- strain not result in two Hfr strains? The cell membranes between the two strands never fuse together. Hfr strains lack fertility factor. Conjugation is typically disrupted before the fertility factor can be transferred. The transferred genes typically recombine with the recipient chromosome. 19. Which of the following is a characteristic of an F+ cell? Ability to synthesize sex pili, presence of a fertility factor, and ability to mate with an F- cell. Ability to synthesize sex pili Presence of a fertility factor Ability to mate with an F- cell

20. What benefit does the F- strain receive from mating with an Hfr strain? It picks up a fertility factor. It can now produce sex pili. It acquires new, potentially beneficial genes from the Hfr strain. It becomes an F+ cell.

21. What is the function of the conjugation pilus? It carries the chromosome of Fcells. It converts F- cells into F+ cells. It contains an F plasmid.

Chapter 7 Homework

It pulls the F+ and F- cells together.

22. What is required by an F- cell to become an F+ cell? F plasmid F+ chromosome Conjugation pilus An F- cell to be a recipient

23. What is the key difference between donor cells and recipient cells? An F plasmid A chromosome Cell membranes Size 24. What cellular macromolecule is the fertility factor comprised of? Nucleic acid Lipid Protein Carbohydrat e 25. 1. 2. 3. 4. 5.

At which point does a recipient cell become an F+ cell? Fusion of the cell membranes Attachment of the sex pilus Transfer of the single stranded F factor Pulling of donor and recipient cells together Formation of the complementary strand of the F factor

Chapter 7 Homework

1 4 3 2 5

26. How does specialized transduction differ from regular lysogeny? The prophage in specialized transduction carries with it pieces of the host chromosomal DNA. The prophage is not excised during specialized transduction. The resulting bacteriophage from specialized transduction does not contain any viral DNA. The resulting bacteriophage from specialized transduction cannot infect a new host cell. 27. What happens to the packaged DNA of a specialized transduced phage when it infects a new recipient cell? The host DNA integrates, with the prophage, into the new recipient chromosome. The DNA is chewed up by enzymes found in the recipient cell. The DNA begins to replicate without integrating into the host chromosome.

28. How can specialized transduction contribute to the transfer of antibiotic resistance genes in a bacterial population? The phage causes the destruction of any antibiotic present during the specialized transduction process. The phage lyses the bacterium and releases resistance genes into the local environment, which can then be taken up by recipient cells.

Chapter 7 Homework

The prophage takes an antibiotic resistance gene with it and is packaged with the newly synthesized viral DNA. 29. Which of the following enzymes is responsible for "unzipping" a DNA molecule in preparation for its replication? primase DNA helicase DNA polymerase DNA ligase

30. Which of the following statements is NOT accurate about prokaryotic and eukaryotic genomes? Most bacteria and archaea have circular DNA in the cytoplasm, while most eukaryotes have linear DNA in the nucleus. Archaea and eukaryotes have histone proteins associated with their DNA, while bacteria do not have histones. All of the DNA in eukaryotic cells is contained within a nucleus. The chromosomes and plasmids in bacteria, archaea, and eukaryotes contain double-stranded DNA.

31. Okazaki fragments are formed because DNA replication __________. is performed by different versions of DNA polymerase in different cells is discontinuous on the lagging strand is semiconservative involves proofreading 32. Which of the following characteristics of a chromosome would identify it as a prokaryotic chromosome rather than a eukaryotic chromosome? It contains histones. It contains A, C, G, and T.

Chapter 7 Homework

It contains double-stranded DNA. It is a circular molecule. Drag the labels onto the diagram to identify the stages in which the lagging strand is synthesized. - DNA polymerase begins synthesizing the lagging strand by adding nucleotides to a short segment of RNA. - After each piece of the lagging strand is complete, it is released from DNA polymerase. - A different DNA polymerase replaces the RNA segments with DNA. - DNA ligase seals the gaps between the pieces, and eventually forms a continuous strand. 33. Semiconservative DNA replication means that the sequence of a DNA molecule is preserved as it is being replicated. each strand of a double-stranded DNA molecule is replicated differently. each daughter DNA molecule is composed of one original strand and one new strand. nucleotides are constantly being recycled as cells make DNA. the cell can proofread its newly synthesized DNA only part of the time. 34. What is the initial target of RNA polymerase? The promoter The terminator region The template DNA 35. RNA polymerase is guided by the template strand of DNA. RNA strand. coding strand of DNA. 36. RNA that has hydrogen bonded to itself forms a termination protein.

Chapter 7 Homework

stem loop. terminator sequence. promoter sequence. 37. How would one increase the concentration of a particular polypeptide in a cell? Increase the amount of DNA Increase the concentration of promoters Increase the level of transcription 38. During elongation, how is the RNA synthesized? Left to right 3’ to 5’ Right to left 5’ to 3’ 39. During the initiation step of translation, the fMet charged tRNA assembles in which site of the ribosome? A site E site P site

40. How does the ribosome know if the entering charged tRNA is correct? The anticodon on the tRNA base pairs to the codon on the mRNA. The preceding amino acid will not permit it to enter the A site.

Chapter 7 Homework

The incorrect tRNA does not fit into the A site.

41. Where would one find an uncharged tRNA molecule in a ribosome? In the A and P sites In the E site In the A site In the P and E sites In the A, P, and E sites In the P site

42. What kind of bond is formed when two amino acids join together? An ionic bond A peptide bond A polar bond A hydrogen bond 43. How is translation terminated? When a protein called a release, factor enters and binds to the A site When there are no more charged tRNA molecules When the A, P, and E sites are all filled When the ribosome runs out of the mRNA

44. Which enzyme breaks the hydrogen bonds during replication? Stabilizing

Chapter 7 Homework

proteins Replication fork ATP DNA helicase 45. How do stabilizing proteins work on the DNA? They bind to the double-stranded DNA. They form the replication fork. They bind to the single-stranded DNA. They use ATP to break the hydrogen bonds. 46. In which direction does the replication fork move? It moves ahead of the unzipped DNA. It moves from the double-stranded DNA to the single-stranded DNA. It moves towards the stabilizing proteins. It moves ahead of the newly synthesized DNA.

47. What ensures that the single strands of DNA do not come back together? ATP DNA helicase Stabilizing proteins The replication fork

Chapter 7 Homework 48. A bacterial genome is typically multiple circular DNA molecules. a single linear piece of DNA. a linear RNA molecule. multiple linear pieces of DNA. a single circular DNA molecule. 49. Which of the following is characteristic of prokaryotic genomes but NOT eukaryotic genomes? enclosed in a nuclear membrane linear chromosomes histones circular chromosomes typically consist of a few to several chromosomes...