Microbiology 225



1. The genetic constitution of an organism is its _______________ while the characteristics displayed by an organism in a given environment comprise the _______________ of the organism.

2. Bacteria are called _______________ because they contain one or sometimes several identical chromosomes, but never pairs of chromosomes.

3._______________ protect bacterial cells from foreign DNA entering into them.

4. The deletion or addition of one or more nucleotides in a DNA molecule causes a misreading of the codons and is termed a _______________mutation.

5. _______________ is a simple, inexpensive, and quick microbiological test for potential carcinogens.

6. The ___________is an appendage on a donor cell that attaches to a recipient cell during conjugation.

7. Compounds that resemble the chemical structure of nitrogen bases closely enough that they are incorporated into DNA and result in mutations are know as _______________ .

8. Bacterial viruses are also called_______________.

9. Chemical or physical agents that increase the frequency of mutations are called _______________ .

10. An__________is a bacterium that requires a growth factor in order to grow, while a_____________does not require a growth factor.

11. A change in the nucleotide sequence of DNA that results in a recognizable change in the organism is called a _______________.

12. DNA that may exist either extrachromosomally or as part of the chromosome is termed an_______________.

13. _____________ is the process by which a cell phenotype changes back to its original state through a mutation.

14. ___________are special segments of DNA that can move from one site in a DNA molecule to another. Another name for these special segments is _______________.


1. The genome of an organism includes genes from

a. chromosomes
b. nucleotides
c. plasmids.
d. a and b
e. a and c

2. Genotypic changes are rare and usually involve only a few cells in a population while phenotypic changes will involve almost all of the cells in a population.

a. True
b. False

3. In the Ames test for mutagens, extract of rat liver is added to the test because

a. it is a good source of nutrients.
b. the extract can convert test compounds to active carcinogens.
c. it contains mRNA necessary for the test.
d. it neutralizes toxic materials in the test.
e. it contains DNA necessary for the test.

4. Resistance to many antibiotics is carried on

a. R factor plasmids.
b. sex pili.
c. enzymes.
d. chromosomes.
e. A factor plasmids.

5. Ultraviolet light is selectively absorbed in the cell by

a. enzymes.
b. DNA.
d. proteins.
c. cell membranes.
e. RNA.

6. Which of the following chemical mutagens will result in the addition of nucleotides to the DNA?

a. base analogs
b. alkylating agents
c. intercalating agents
d. nitrous acid
e. All of the above agents.

7. Mutations are expressed more frequently in bacteria because they

a. divide often.
b. are competent.
c. divide infrequently.
d. are diploid.
e. are haploid.

8. The technique of replica plating involves transferring all of the colonies on one plate simultaneously to another plate.

a. True
b. False

9. The segments of DNA transferred between cells are

a. large.
b. single-stranded.
c. small.
d. circular.
e. not functional.

10. Thymine dimer formation is the result of exposing DNA to

a. ultraviolet light.
b. base analogs.
c. transposons.
d. X-rays.
e. intercalating agents.

11. The process of DNA repair in which enzymes cut out a damaged section of DNA and other enzymes then repair the resulting break is known as

a. excision repair.
b. SOS repair.
c. photoreactivation.
d. light repair.
e. DNA cannot be repaired.

12. When bacteria develop resistance to an antibiotic, the antibiotic does not cause the mutation but only selects for a preexisting mutation.

a. True
b. False

13. An organism which requires a growth factor in order to grow is called a(n)

a. prototroph.
b. wild type.
c. autotroph.
d. auxotroph.
e. heterotroph.

14. The Ames test for chemical mutagens

1. is less expensive than animal testing.
2. uses the mutation of a his+ cell.
3. is faster than animal testing.
4. is more expensive than animal testing.
5. uses the reversion of a his- mutant.
6. takes longer than animal testing.
a. 1,2,3
b. 1,3,5
c. 1,2,6
d. 4,5,6
e. 2,4,6

15. Conjugation differs from transformation and transduction in that it requires contact between the donor and the recipient.

a. True
b. False

The genetic code is said to be __________ because more than one codon will specify a particular amino acid.

A. ambiguous
B. degenerate
C. multiplicative
D. repetitious

Which of the following is not considered the final product of the expression of a gene?

A. a polypeptide chain
B. an mRNA molecule
C. a tRNA molecule
D. an rRNA molecule

Scientists study mutations in order to

A. understand more about the nature of genes.
B. understand more about the biochemistry of a particular microorganism.
C. test the carcinogenic potential of a compound by determining the mutagenic capability of it.
D. All of these.

Which of the following types of mutation may play an important role in driving evolution because they are often nonlethal and, therefore, remain in the gene pool?

A. nonsense mutations
B. missense mutations
C. both nonsense and missense mutations
D. neither nonsense nor missense mutations

Mutations that inactivate metabolic pathways are called __________ mutations.

A. morphological
B. biochemical
C. lethal
D. conditional

Mutations that result in the death of an organism when expressed are called __________ mutations.

A. dominant
B. recessive
C. lethal
D. conditional

In order to accommodate all 20 amino acids, it is necessary to read the base sequence in groups of __________.

A. two
B. three
C. four
D. five

A __________ mutation is one that causes premature termination of the synthesis of the protein

A. missense
B. nonsense
C. silent
D. None of these.

A mutation that changes the amino acid sequence of the resulting protein by substitution is called a __________ mutation.

A. missense
B. nonsense
C. silent
D. None of these.

Spontaneous mutations are caused by

A. errors in DNA replication.
B. insertion of transposons.
C. either errors in DNA replication or insertion of transposons.
D. neither errors in DNA replication nor insertion of transposons.

The formation of a new chromosome, different from either parent, by the combination of genetic material from two organisms is called ____________.

A. transformation.
B. conjugation.
C. recombination.
D. transduction.

A reciprocal exchange in which a pair of homologous sequences break and rejoin in a crossover is called __________ recombination.

A. general
B. site-specific
C. replicative
D. None of these.

The nonhomologous insertion of DNA into the chromosome is called __________ recombination.

A. general
B. site-specific
C. replicative
D. None of these.

The incorporation of a single strand to form a stretch of heteroduplex DNA is called __________ recombination.

A. general
B. site-specific
C. replicative
D. None of these.

A donor DNA that enters the bacterium by one of several mechanisms is called a(n):

A. merozygote
B. exogenote
C. endogenote
D. None of these.

The genome of a recipient cell is called a(n) __________.

A. merozygote
B. exogenote
C. endogenote
D. None of these.

A recipient cell that is temporarily diploid for a portion of the genome during the replacement process is called a(n) __________.

A. merozygote
B. exogenote
C. endogenote
D. None of these.

The elimination of a plasmid either spontaneously or by treatments that inhibit plasmid replication without affecting host cell reproduction is called

A. transformation.
B. conjugation.
C. curing.
D. plasmolysis.

Plasmids that have genes for resistance to antibiotics are called __________ factors.

A. col
B. resistance
C. virulence
D. metabolic

__________ plasmids make a bacterium pathogenic by conferring resistance to host defenses or by encoding the production of a toxin.

A. Col
B. Resistance
C. Virulence
D. Metabolic

Which of the following is not true about transposable elements?

A. They move about the chromosomes within an organism.
B. They lack the infectious cycle of temperate phages.
C. They reproduce independently like plasmids.
D. All of these are true about transposable elements.

Which of the following is not an effect of transposable elements?

A. insertional mutagenesis
B. termination of translation and/or transcription by insertion of stop codons
C. insertional activation
D. All of these are effects of transposable elements.

In an F+ X F- conjugation, the donor is the __________ strain.

A. F+
B. F-




C. both F+ and F- (It is a reciprocal exchange.)

D. neither F+ nor F- (There is no exchange.)

Which of the following matings can take place?

A. F+ X F+
B. Hfr X Hfr
C. Hfr X F+
D. None of these.

Complete transfer in an Hfr X F- mating takes approximately __________ minutes.

A. 20
B. 50
C. 100
D. 200

An F'' plasmid results when

A. an F+ X F- mating is interrupted before completion.
B. an Hfr X F- mating is interrupted before completion.
C. an integrated F plasmid is incorrectly excised, bringing host genes with it.
D. None of these.

Which of the following matings can take place?

A. F'' X F-
B. F' X Hfr
C. F' X F+
D. None of these.

F'' X F- conjugation is called

A. transduction.
B. sexduction.
C. F-duction.
D. transformation.

When a recipient cell acquires a piece of naked DNA from the environment, it is called

A. conjugation.
B. transformation.
C. transduction.
D. transfection.

When bacterial genes are transferred to another bacterium by a virus, it is called

A. conjugation.
B. transformation.
C. transduction.
D. transfection.

The frequency of cotransfer of two genes can be used to construct __________ maps indicating

the distance of two genes from each other.
A. transformation
B. generalized transduction
C. either transformation or generalized transduction
D. neither transformation nor generalized transduction

Which of the following cannot be used to cure a bacterial strain of its plasmids?

A. UV and/or ionizing radiation
B. acridine mutagens
C. thymine starvation
D. All of these can be used to cure plasmids.

Proteins produced by bacteria that destroy other bacteria are generally called

A. colicins.
B. bacteriocins.
C. bacteriolysins.
D. plasmolysins.

Who is credited with demonstrating the existence of mating types in bacteria?

A. Hayes
B. Lederberg
C. Tatum
D. None of these.

Transfer of genetic information via direct cell-cell contact is called

A. transformation.
B. transduction.
C. transfection.
D. conjugation.

Specialized transduction can be carried out by

A. any bacteriophage.
B. any temperate bacteriophage.
C. only those temperate bacteriophages that integrate into the host chromosome.
D. All of these.

When DNA from a wild type and a mutant strain are reannealed, homologous regions pair normally but mutant regions bubble; this process, known as __________ mapping, can be used to map the location of the mutant genes.

A. denaturation
B. heteroduplex
C. restriction endonuclease
D. hybridoma

Which of the following is true of the integration of a viral genome into the host chromosome?

A. It is a form of site-specific recombination.
B. The enzymes are specific for the virus and its host.
C. Both of these answers are true.
D. Neither of these answers is true.

Which of the following is not a possible fate for an exogenote?

A. integration into the host chromosome
B. independent replication and functioning
C. survival without replication
D. All are possible fates of exogenotes.

Transposable elements that carry genes for functions other than those needed for transposition (e.g., antibiotic resistance) are called

A. insertion sequences.
B. composite transposons.
C. either insertion sequences or composite transposons.
D. neither insertion sequences nor composite transposons.

In an HFR , F+ mating the conjugation bridge usually breaks before chromosomal transfer is complete. Therefore, the recipient remains F-.

In the mechanics of conjugation, exclusive of gene transfer, Hfr and F+ strains behave the same.

The entire genome can be mapped because the conjugation bridge usually stays intact long enough for the entire chromosome to be transferred.

Transposable elements have been found only in procaryotes and do not appear to play a major role in eucaryotic genetics.

Each antibiotic resistance gene is carried on a single plasmid.

Hfr strains can be used to map the entire bacterial genome by constructing overlapping maps from Hfr strains with different integration sites.

When a genome is mapped with Hfr conjugation, a high frequency of gene transfer means that the gene is located close to the integration site of the plasmid.

Transformation has been observed in only a limited number of species in nature, but we have found ways to force the process upon other species in the laboratory.

A __________ is a latent form of a virus genome that remains within the host without destroying it.

A __________ is a piece of extrachromosomal DNA that has its own replication origin.

A plasmid that can either exist independently of the chromosome or be integrated into it is called a(n) __________.

Plasmids that have genes for pili and can transfer copies of themselves to other bacteria during conjugation are called __________ plasmids.

__________ is the process by which some cells are incapable of receiving an exogenote.

__________ plasmids carry genes for enzymes that degrade environmental substances such as aromatic compounds or pesticides.

All resistance plasmids are nonconjugative.

Transfer of genes from one mature independent organism to another is called:

A. horizontal gene transfer
B. lateral gene transfer
C. vertical gene transfer
D. orthogonal gene transfer

Transfer of genes from parent to offspring is called

A. horizontal gene transfer
B. lateral gene transfer
C. vertical gene transfer
D. orthogonal gene transfer

The process of _____________ involves identifying open reading frames (ORFs), determining potential amino acid sequences, and comparing these to those of known proteins.

A ____________ is a long sequence of nucleotides that has been determined by analysis of overlaps between shorter sequenced fragments.

Which of the following is the most error-prone of the repair mechanisms?

A. postreplication repair
B. recombination repair
C. SOS repair
D. All are equally error-prone.