Ch. 16 micro

DNA polymerase is able to correct mistakes by proofreading because it has _____.

3' to 5' exonuclease activity

Which two of these bacterial mutants could be selected by exposing them to a particular stress condition and looking for growth?

A mutant resistant to a particular antibiotic A mutant resistant to bacteriophage infection

Replica plating would be most useful for the detection of which of these types of bacterial mutants?`

A mutant unable to synthesize lysine

Which three types of mutations are classified as reversion mutations?

A second mutation creates a codon that replaces the wild type amino acid with a similar amino acid. A second mutation that creates a new codon that codes for the wild type amino acid. A second mutation that restores the original wild-type sequence.

Thymine dimers can be corrected by photoreactivation, which is a type of

Blank 1: direct

Match each bacterial species with a correct statement regarding its transformation. Instructions

Choice, becomes competent in stationary growth phase becomes competent in stationary growth phase Haemophilus influenzae matches Choice, transformation requires a specific, 9 base pair sequence that appears >1400 times in its genome transformation requires a specific, 9 base pair sequence that appears >1400 times in its genome Neisseria spp. and Thermus spp. matches Choice, constitutively competent constitutively competent

Compared to other types of testing, which three of the following are advantages to the Ames test for screening potential mutagens?

It is inexpensive It can reduce the numbers of animals needed for testing It is fast

In the methyl-directed mismatch repair system of E. coli, after a mismatch is identified, the enzyme _____ cuts the non-methylated strand and an exonuclease digests it. The gap is later filled in by DNA polymerase and sealed by DNA ligase.

MutH

In the methyl-directed mismatch repair system of E. coli, mismatches are identifi

MutS

What effect would you expect from a mutation in the -35 region of the lac operon promoter?

No expression regardless of the carbon source available

Which process is shown in the diagram?

Rolling-circle replication

Which of the following is depicted in the diagram?

Slippage leading to a deletion

Why are transversion mutations more rare than transition mutations?

There are steric problems with pairing purines with purines.

How do intercalating agents induce DNA mutations?

They insert between stacked bases of the helix.

True or false: DNA proofreading enzymes do not always correct replication mistakes.

True

Oxygen free radicals convert guanine to 8-oxo-7,8-dihydrodeoxygu

adenine

DNA that has been damaged by exposure to the mutagen methyl-nitrosoguanidine can be directly repaired by which enzyme?

alkyltransferase

Adenine or guanine nucleotides can lose their base, resulting in a(n) ______.

apurinic site

Cytosine or thymine nucleotides can lose their base, resulting in a(n) ______.

apyrimidinic site

Match each example of a chemical mutagen with the type of DNA damage it can cause.

base analogue that causes mismatching intercalating agent hydroxylates cytosine alkylating agent deaminates bases

The image illustrates which type of DNA repair?

base excision repair

Which three of the following are RecA activities during an SOS re

causing LexA to undergo autoproteolysis taking on a coprotease function binding to single- or double-stranded DNA breaks

Mutations in a promoter region that affect the ability of RNA polymerase to initiate transcription include _____. [Choose two.]

changing the sequence of the -35 region changing the spacing between the -35 and -10 regions

Match each component of the E. coli mismatch repair system with its function.

connects the newly synthesized DNA with the old DNA replaces nucleotides that were excised removes DNA around a mismatch scans newly replicated DNA for mismatches

Which one of these types of DNA damage is most likely to be corrected by base excision repair?

damaged or unnatural bases

Virulence factors are gene products involved in the production of _____.

disease

Arrange these steps in natural bacterial transformation in order.

double strand one double protein chromosome

True or false: The Ames test is used to directly screen chemicals for carcinogenicity

false

Which three of the following are characteristics of the tester strains used in the Ames test for mutagenic chemicals?

genus Salmonella defective in DNA repair cell walls are permeable to test substances

Thymine can exist in a rare enol form tha

guanine

Thymine can exist in a rare enol form that can base pair with the abnormal partner ____.

guanine

The Salmonella enterica bacteria that are used as tester strains in the Ames test have mutations in the operon that controls the biosynthesis of what amino acid?

histidine

Base analogues induce DNA mutations by _____.

incorporating into the growing DNA chain

Chemical mutagens that are planar and insert themselves between stacked bases of the DNA helix are called

intercalating

When the mismatch repair system of E. coli detects mismatched bases, new strands can be distinguished because they are not _____.

methylated

The diagram illustrates which type of DNA repair?

mismatch repair

Which of these types of point mutation is most likely to drive evolution because they are not lethal and remain in the gene pool?

missense

Match each type of mutation with the appropriate example. Instructions

mutant cannot synthesize an essential molecule such as an amino acid phenotype is only affected at high temperatures mutation affects the appearance of colonies mutant is not affected by a particular pathogen or chemical

Which type of DNA repair is shown in the diagram?

nucleotide excision repair

Activating the SOS response means activating _____ genes.

over 50

The structure and/or activity of ribosomes would most likely be affected by a mutation in a gene coding for ______.

rRNA

Match each fate of donor DNA taken up by a bacterial cell with the most likely outcome. Instructions

recombinant genome replicates, forming a population of stable recombinants donor DNA replicates independently, forming a population of stable recombinants donor DNA is eventually lost after many rounds of cell division; no stable recombinants donor DNA is degraded; no stable recombinants

A mutation in the operator site of the lac operon that prevents the lac repressor protein from binding, is considered a mutation in a _____.

regulatory sequence

The technique shown in the image is _______.

replica plating

Which one of these techniques would be most useful in attempting to isolate a tryptophan auxotroph?

replica plating

The use of a detection system to locate a microbe with a particular mutant phenotype is generally known as ____.

screening

The diagram illustrates the genetic changes that result from different types of mutations. Match the letter of each type of mutation with the appropriate name. Instructions

silent missense nonsense frameshift

A mutation in a gene encoding a tRNA would exhibit a phenotype of _____.

slow growth

When setting up an Ames test, a small amount of histidine is added to the agar because _____.

some bacterial replication is required for development of a mutation.

When the mismatch repair system of E. coli detects mismatched bases, it is able to determine the strand that needs repair, because _____ is methylated.

the old strand

Missense mutations provide variation within a population and drive evolution because _____.

they are not lethal and remain in the population gene pool

Guanine can exist in a rare enol form that can base pair with the abnormal partner ____.

thymine

UV radiation can cause mutations by inducing ______.

thymine dimers

Which of these types of DNA damage are usually mended by direct DNA repair?

thymine dimers alkylated bases

Which two of the following are types of DNA damage that are corrected by nucleotide excision repair?

thymine dimers distortions in the double helix

The process shown in the diagram is ______.

transformation

Which bacterial process is illustrated by the image

transformation

Select the three major mechanisms of horizontal gene transfer in bacteria.

transformation transduction conjugation

Bacteria that are lysine auxotrophs (unable to synthesize lysine) can be detected by first culturing them on a solid medium supplemented with lysine, then transferring those colonies to a plate lacking lysine -- a technique called

Blank 1: replica

Which type of chemical agent converts guanine to 8-oxo-7,8-dihydrodeoxyguanine?

Oxygen free radicals

The diagram shows which of the following?

Slippage leading to an insertion

What would be the effect of a mutation in the operator sequence of the lac operon, so that the lac repressor protein could not bind?

The operon would be continuously transcribed.

The mismatch repair system of E. coli is able to detect mismatched bases because, for a short time, newly synthesized DNA strands are _____.

unmethlyated