General Instructions: Answer multiple choice questions on the test sheet. Answer other questions in the space provided on the test sheet. Be sure that you answer the question in complete sentences. Write your name on all pages of the test.
Multiple Choice (2 pts each). Choose the most correct answer and mark the corresponding letter on the blank provided to the left of the question.

E 1. The time required for the formation of two cells from one cell is called _____.
A. the generation time
B. the doubling time
C. the growth rate
D. the dilution rate
E. A and B

D 2. Given a population of bacteria with an initial population of 5 x 10⁷ cfu/ml and a population of 8 x 10⁸ cfu/ml after 1 hour. What is the doubling time of this culture?
A. 0.5 hours
B. 1 hour
C. 2 hours
D. 0.25 hours
E. 4 hours

E 3. Bacterial populations increase in size by _________.
A. meiosis
B. mitosis
C. fusion
D. replication
E. binary fission

B 4. Hydrogen peroxide is a potentially toxic compound generated during aerobic respiration. Which of the following enzymes degrades hydrogen peroxide to water and oxygen?
A. super oxide dismutase
B. catalase
C. hydrogenase
D. nitrogenase
E. oxidase

C 5. During which phase of the growth curve might secondary metabolites (e.g., toxic compounds) be produced and growth occur without a net increase in the viable count?
A. lag
B. exponential
C. stationary
D. death
E. log

A 6. True (A) or False (B). In a chemostat, the population density is controlled by the nutrient concentration and the growth rate is controlled by the dilution rate.

D 7. Which of the following methods for assaying microbial growth in broth culture is simplest and most convenient?
A. microscopic counts
B. plate counts
C. cell nitrogen
D. turbidity
E. oxygen uptake

B 8. The temperature of the interior portion of a "hot" compost pile might be 65 to 70 ^oC. What type of bacteria grows at these temperatures?
A. psychrophile
B. thermophile
C. mesophile
D. extreme thermophile
E. psychrotroph

C 9. Dried fruit with a water activity (aw) = 0.7 might be spoiled (colonized) by which of the following?
A. halophile
B. osmophile
C. xerophile
D. psychrophile
E. None of the above.

E 10. Which of the following types of bacteria require oxygen for growth?
A. aerobes
B. facultative anaerobes
C. microaerophiles
D. anaerobes
E. a and c

B 11. True (A) or False (B). Dry heat is more effective at killing bacteria than moist heat.

D 12. Which of the following are the correct parameters for an autoclave to sterilize a small amount (1 liter) of medium?
A. 121^oC at atmospheric pressure for 15 minutes
B. 212 ^oC at atmospheric pressure for 10 minutes
C. 100 ^oC at 100 lbs/sq inch for 5 minutes
D. 121 ^oC at 15 lbs/sq inch for 15 minutes
E. None of the above are correct.

B 13. True (A) or False (B). A bactericidal agent only inhibits the growth of bacteria.

E 14. Which of the following would be the most appropriate means to sterilize heat labile vitamins?
A. autoclaving
B. filter sterilizing
C. boiling
D. UV irradiation
E. B and D

A 15. Which of the following classes of antibiotics does not inhibit protein synthesis?
A. [beta]-lactams
B. aminoglycosides
C. macrolides
D. tetracycline
E. All of the above inhibit protein synthesis.

B 16. True (A) or False (B). Bacteriological medium can be sterilized by autoclaving for less than 15 minutes without regard to the volume of medium being sterilized.

B 17. Which of the following is best suited for reducing spoilage of fresh meat prior to shipment?
A. boiling
B. irradiation
C. phenol treatment
D. autoclaving
E. All of the above.

A 18. Penicillin inhibits _______
A. bacterial cell wall synthesis
B. bacterial protein synthesis
C. fungal cell wall synthesis
D. DNA replication
E. glycolysis

C 19. The decimal reduction time is ______.
A. the time required to kill all cells in a population at a given temperature
B. the time required to kill all cells in an autoclave
C. the time required to reduce the population of bacteria tenfold at a given temperature
D. the time required for a population to increase by tenfold
E. None of the above is correct.

A 20. True (A) or False (B). Ionizing radiation sterilizes materials by producing highly reactive hydroxyl radicals that react with and damage DNA and other macromolecules.

D 21. Which of the following statements about DNA is incorrect?
A. DNA is composed of the four nucleotides adenine, guanine, cytosine, and thymine.
B. DNA is a double helix composed of two polynucleotides held together by hydrogen bonds.
C. The two polynucleotides have an antiparallel orientation.
D. The nucleotides are joined together by sulfhydryl bonds.
E. The polynucleotides have a sugar phosphate backbone.

D 22. According to the "Central dogma of molecular biology", information flows from ______.
A. RNA through DNA to protein.
B. protein through RNA to DNA
C. DNA through protein to RNA
D. DNA through RNA to protein
E. RNA through protein to DNA

A 23. The ratio of guanine to cytosine nucleotides in cellular DNA is ____.
A. 1:1
B. 2:1
C. 4:1
D varies with the species of bacteria
E. None of the above.

D 24. _____ catalyzes the reaction between the incoming deoxynucleotide and the growing end of DNA and proofreads each inserted nucleotide.
A. DNA helicase
B. DNA gyrase
C. DNA polymerase I
D. DNA polymerase III
E. DNA ligase

B 25. True (A) or False (B) - Incoming nucleotides are added to the 5-prime phosphate group of the growing polynucleotide during DNA replication.

B 26. Which of the following statements about RNA is incorrect?
A. RNA acts at both the genetic and functional levels.
B. The sole difference between DNA and RNA is that ribose, rather than 2- deoxyribose, is present only in DNA.
C. RNA is the product of transcription carried out by RNA polymerase.
D. Only mRNA is translated into a polypeptide.
E. tRNA are the smallest RNA molecules.

B 27. True (A) or False (B). Okazaki fragments are synthesized towards the replication fork on the leading strand.

D 28. The minimum number of nucleotides on a strand of DNA required to code for a polypeptide consisting of 150 amino acids would be ____.
A. 50
B. 150
C. 300
D. 450
E. 600

A 29. True (A) or False (B). More than one codon may code for a specific amino acid, but no codon may code for more than one amino acid.

A 30. If the anticodon of a tRNA carrying serine is AGU then the codon in the mRNA is ____ and the corresponding DNA sequence is ______.
A. UCA / AGT
B. AGU / UCA
C. UCA / UCA
D. AGU / AGU
E. ACU / TGA

B 31. A major mechanism for the control of enzyme activity involving regulation of pre-existing enzymes is _____.
A. operon control
B. feedback inhibition
C. global control
D. sigma replacement
E. all of the above.

B 32. Enzymatic activity of a pathway (e.g., biosynthesis of an amino acid) can be controlled by the endproduct inhibiting the transcription of the genes involved in the synthesis of the amino acid. This is referred to as _________.
A. saturation
B. enzyme repression
C. positive control
D. substrate inhibition
E. feedback inhibition

D 33. The repressor protein regulates the lactose operon by ________.
A. repressing the activity of pre-existing enzymes
B. blocking transcription of protein from a mRNA
C. blocking DNA synthesis during transcription
D. blocking transcription of the operon by RNA polymerase
E. None of the above.

B 34. Enzymes whose level of synthesis is constant under all growth conditions are called _____.
A. allosteric enzymes
B. constitutive enzymes
C. global enzymes
D. positively regulated enzymes
E. negatively regulated enzymes

B 35. The repression of the lactose operon by the presence of glucose is mediated through ________.
A. elevated level of cyclic AMP in the cell
B. depressed levels of cyclic AMP (cAMP) in the cell
C. a lac repressor /glucose complex binding to the lac operator
D. glucose binding to the lac operator
E. None of the above.

D 36. Unrelated genes required for the survival of carbon starvation are scattered throughout the chromosome of Escherichia coli and are under control of the same global regulatory protein. These genes are part of a(n) _____.
A. operon
B. regulon
C. exon
D. modulon (syn. stimulon)
E. none of the above

E 37. Which of the following statements is False about cells in the early part of the second phase of diauxic growth in a glucose/lactose based medium?
A. The lac repressor is bound to the inducer and cannot bind to the operator region.
B. The levels of cyclic AMP are elevated relative to the first phase of growth.
C. The lac operon is induced.
D. cAMP/CAP is bound to the CAP binding site.
E. All of the above statements are true.

E 38. Repression of the lac operon by glucose is referred to as __________.
A. catabolite repression
B. catabolite activation
C. derepression
D. glucose effect
E. A and D

B 39. True (A) or False (B). The above figure illustrates diauxic growth.

A 40. True (A) or False (B). Different sigma factors may act as global regulators of gene expression.

E 41. A mutant strain of Escherichia coli that requires an amino acid for growth is called a ___.
A. autotroph
B. lysogen
C. prototype
D. prototroph
E. auxotroph

A 42. A mutation has occurred which is readily reversible to restore the original parental phenotype. This mutation is most likely due to a ______.
A. base-pair substitution
B. microdeletion
C. microinsertion
D. pyrimidine dimer
E. None of the above.

E 43. Consider a mutation which occurs in which the change is from UAC to UAU, where both triplets code for the amino acid tyrosine. This is an example of a _____.
A. silent mutation
B. nonsense mutation
C. missense mutation
D. a point mutation
E. A and D

B 44. True (A) or False (B). Ultraviolet light is a form of ionizing radiation that produce radicals that react with macromolecules such as DNA.

B 45. _______ are cells capable of taking up DNA from the environment.
A. Conjugative cells
B. Competent cells
C. Transducing cells
D. Hela cells
E. Minicells

E 46. Plasmids may code for all of the following functions except ____.
A. antibiotic resistance
B. toxins
C. bacteriocins
D. catabolic pathways
E. All of the above are coded for by plasmids

A 47. True (A) or False (B). Only the donor cell (F⁺) make sex pili for conjugation.

48-50. Match each term with the appropriate statement (A-E) about it.

The following questions are each worth 10 pts. Write or draw your answers on the sheet of paper provided.
51. Consider an inducible operon such as lac operon and a repressible operon such as arginine operon.
A. Draw the state of each operon when the respective inducer and co-repressor is present in excess amounts in the cell. Be sure to label the promoter, operator, structural genes, repressor, and corepressor (or inducer)

Lactose is present - lactose binds to repressor and the lac/repressor does not bind to the operator and transcription occurs.

Agrinine is present and it binds to the repressor which now binds to the operator and blocks transcription.

B. Draw the state of each operon when the respective inducer and co-repressor is absent from the cell. Be sure to label the same elements listed above where appropriate.

Lactose absent - repressor binds to operator and transcription is blocked

Arginine absent and the repressor does not bind to the operator and transcription occurs.

52. Identify or define each of the following terms:

F⁺ cell - male, F plasmid-donor cell

F ^- cell - female, plasmid-recipient cell

Hfr cell - male, F plasmid integrated into chromosome

F-prime - male, F plasmid integrated and excised from chromosome. F plasmid contains a bit of chromosome.