Microbiology Chapter 8: Bacterial Genetics

Place the following events in the process of virus replication and the generation of a transducing particle in the correct order.

1. A bacteriophage 2. The phage DNA 3. Enzymes encoded 4. Phage nucleic acid 5. During construction of viral particles

Place the correct sequence of experiments in order to better understand the Griffith Experiment for Transformation.

1. Living encapsulated cells = mouse dies 2. Living non-encapsulated cells + heat-killed encapsulated cells = no effect 3. heat-killed encapsulated cells + living non-encapsulated cells = mouse dies + living encapsulated cells isolated

Please match each type of mutation with its appropriate description. 1. A mutation that changes a codon that specifies an amino acid to a stop codon, resulting in premature termination of polypeptide synthesis. 2. A mutation that results in changing a codon such that a different amino acid is specified. 3. A mutation that changes a codon into a different codon, but both codons specify the same amino acid; this causes no change in the resulting polypeptide. 4. A mutation resulting from an insertion or deletion of bases that causes a change in the reading frame of the mRNA.

1. Nonsense mutation 2. missense mutation 3. silent mutation 4. frameshift mutation

Match the mutation with the correct name.

1. Silent mutation 2. missense mutation 3. nonsense mutation

A culture of E. coli is irradiated with UV light. The UV light affects the cell's DNA by: A. deleting essential bases needed for protein synthesis. B. forming covalent bonds between thymine bases on the same strand of DNA. C. forming covalent bonds between cytosine and guanine bases. D. joining the two strands of DNA together by covalent bonds. E. joining the two strands of DNA together by hydrogen bonds.

B. forming covalent bonds between thymine bases on the same strand of DNA.

True or False: A missense mutation has a greater impact on a cell than does a frameshift mutation.

False

Which of the following types of repair does not require the standard DNA polymerase with proof-reading capability? a. Light repair b. Proofreading c. SOS repair d. Mismatch repair e. Excision repair

a. Light repair

What would be the consequence of a transposon inserting into the site shown by the red arrow? a. The bacterium would likely become sensitive to tetracycline. b. The bacterium would not be able to conjugate with other bacteria. c. The tetracycline gene would be activated and the bacterium would be resistant to that antibiotic. d. The bacterium would no longer be able to undergo binary fission. e. The bacterium would likely become sensitive to all antibiotics.

a. The bacterium would likely become sensitive to tetracycline.

Horizontal gene transfer can occur via: a. conjugation b. mutation c. binary fission d. mitosis

a. conjugation

Bacterial cells that have been genetically modified to carry an antibiotic resistance gene can be separated from susceptible (non-resistant) microbes by using a _______ selection method using agar plates with antibiotic. a. direct b. indirect c. spread plate d. pour plate

a. direct

Indirect selection: a. is necessary to isolate auxotrophic mutants. b. uses media on which the mutant but not the parental cell type will grow. c. uses media that reverses the mutation. d. uses media upon which neither the parental cell type nor mutant grows.

a. is necessary to isolate auxotrophic mutants.

Direct selection involves inoculating cells onto growth media on which: a. the mutant but not the parental cell type will grow. b. the mutation will be reversed. c. the nutrients necessary for mutation to occur are present. d. the mutagen is present.

a. the mutant but not the parental cell type will grow.

Preventing the function of light repair (photoreactivation) interferes with the repair of which of the following? a. thymiders b. thymine dimers c. nonsense mutations d. frameshift mutations e. mismatched bases f. oxidized guanine

b. thymine dimers ??

Which change in a gene's DNA sequence would have the least effect on the eventual amino acid sequence produced from it? a. Deletion of two consecutive nucleotides b. Addition of one nucleotide c. Addition or deletion of three consecutive nucleotides d. Substitution of one nucleotide AND addition of one nucleotide

c. Addition or deletion of three consecutive nucleotides

DNA transfer by conjugation is more efficient in a liquid medium setting, subjected to very mild agitation (stirring), rather than on an agar plate format. Why? a. Direct cell-to-cell contact is required for this process, and this is more likely to be achieved in the plate format than in the fluid format (especially for relatively non-motile types of bacteria). b. Direct cell-to-cell contact isn't required for this process, so the ability to secrete the DNA into the surrounding fluid medium makes the process more efficient than the dry surface of an agar plate. c. Direct cell-to-cell contact is required for this process, and this is more likely to be achieved in the fluid liquid format than on an agar plate (especially for relatively non-motile types of bacteria). d. Trick question-it can take place with the same degree of efficiency on either format. It doesn't matter!

c. Direct cell-to-cell contact is required for this process, and this is more likely to be achieved in the fluid liquid format than on an agar plate (especially for relatively non-motile types of bacteria).

Which of the following pairs is NOT correctly matched? a. Ethidium bromide - chemical mutagen b. Mutagen - induces mutations c. Nonsense mutation - incorrect amino acid d. Transposons - "jumping genes" e. Phenotype - observable characteristics

c. Nonsense mutation - incorrect amino acid

Transposons can cause mutations by: a. replacing specific nucleotides in the original DNA. b. None of the above - transposons cannot cause mutations. c. inducing uncontrolled binary fission. d. "jumping" into a gene and disrupting its function.

d. "jumping" into a gene and disrupting its function.

To maximize the number of thymine dimer mutations following UV exposure, should you keep human cells in tissue culture in the dark, in the light, or does it matter at all? a. The dark-light will activate the photorepair systems that can break thymine dimers induced by UV light. b. The light-it's important to keep on producing the thymine dimers by keeping the plate exposed to light as much as possible. c. It's best to alternate light and dark every hour to increase the chances that thymine dimers will form in the human cells, but still keep the photorepair systems from correcting them as they are formed. d. It doesn't matter-human cells don't have the enzymes needed for photorepair of thymine dimers.

d. It doesn't matter-human cells don't have the enzymes needed for photorepair of thymine dimers.

Repair mechanisms that occur during DNA synthesis are 1. mismatch repair 2. proofreading by DNA polymerase 3. light repair 4. excision repair 5. SOS repair a. 3 and 4 b. 2 and 3 c. 4 and 5 d. 1 and 3 e. 1 and 2

e. 1 and 2

On which of the following DNA strands will UV light have the most effect? a. CAGTGCTAGC b. ATCCGTGCAT c. GACUUCGAGG d. ACTACTACTG e. ACTTGCTTAC f. CAATCATCCT

e. ACTTGCTTAC ??