Module 4b part 2

A key component of the SOS response is the destruction of a transcriptional repressor protein called _______.

LexA

Which approach would be used to screen for revertants from a lysine auxotroph?

Plate a large number of lysine auxotrophs on a minimal medium lacking lysine.

When DNA damage is so great that DNA synthesis stops, a control system called the ________ response occurs

SOS

True or false: A mutation can prevent a gene from being expressed, even if the coding sequence is completely unchanged.

True

A suppressor mutation, which returns a mutant back to its wild-type phenotype, occurs at ______the first mutation.

a different site from

Alternative forms of a gene are called

allele

The lambda phage of E. coli is a temperate bacteriophage, meaning that it _________.

can insert its genome into the host chromosome

In bacteria, conjugation refers to the transfer of DNA by ________.

cell to cell contact

In bacteria, conjugation refers to the transfer of DNA by Blank______.

cell-to-cell contact

Antibiotic resistance genes like those found on R plasmids often code for enzymes that ________.

destroy or modify antibiotics

Spontaneous mutations can occur when a nitrogenous base shifts to a different isomer, also called a(n) Blank

tautomeric form

The process of taking up DNA from the surroundings, and maintenance of the DNA in a heritable form, is called

transformation

DNA segments that can repeatedly insert into one or more sites or into one or more genomes are called

transposable genetic

The most prevalent form of a gene, and its associated phenotype, is called the ____ type

wild

A wild-type chemoorganotroph like E. coli able to grow on a minimal medium containing only salts and a carbon source is known as a(n) ___________. These wild-type strains may give rise to mutants incapable of survival without additional nutrients, like a particular amino acid.

Prototroph

Which three statements regarding homologous recombination are correct?

RecA protein is involved. Similar or identical DNA strands are broken and reunited. It is the most common mechanism of DNA recombination.

Which example of a missense mutation in a protein-encoding gene would most likely be a neutral mutation?

Replacement of a polar amino acid with another polar amino acid at the protein's surface

Match each protein or protein complex involved in mismatch DNA repair with its function.

Scan newly replicated DNA for mismatchesSeparate the parental and new DNA strands around a mismatchProtect the methylated (parental) DNA strandSynthesize DNA complementary to the methylated (parental) strand

Some instances of antibiotic resistance occur by spontaneous chromosomal mutation. In these cases, the mutation results in

a change in the drug target such that the drug can no longer bind

A genetic selection differs from a genetic screen in that __________.

a genetic selection adjusts the environment so that only mutants of the desired phenotype can grow

Select two examples of mutations that affect regulatory sequences of microbial genes.

a mutation in a promoter so that RNA polymerase cannot bind a mutation in the lac operator so the lac repressor cannot bind

In simple transposition, a mobile genetic element ________.

excises from one location and inserts in a different location in the same genome

Which type of DNA repair corrects damage (e.g., thymine dimers) that causes distortions in the DNA double helix?

excision repair

William Hayes' 1952 experiments demonstrated that conjugation is unidirectional and identified strains he named F+ and F-. The "F" stands for

fertile

A mutation that leads to a change from wild type to a mutant form is called a(n) ______ mutation

forward

Mutations that arise from the insertion or deletion of 1 or 2 base pairs within the coding region of a gene are called _______ mutations

frameshift

The major conclusion of Hayes' 1952 experiments, which demonstrated the existence of F+ and F- strains, was that __________.

he major conclusion of Hayes' 1952 experiments, which demonstrated the existence of F+ and F- strains, was that

Hfr strains of bacteria are so named because they undergo a __________ (high/low) frequency of ___________.

high, recombinants

The most common type of DNA recombination (e.g., during meiosis or bacterial horizontal gene transfer) is _________ recombination between similar or identical DNA strands.

homologous

Drug resistance often arises when bacteria gain new properties by acquiring genes from other bacteria. This process is known as _______ gene transfer.

horizontal

Drug resistance often arises when bacteria gain new properties by acquiring genes from other bacteria in the process known as

horizontal gene transfer

In this diagram illustrating F-factor-mediated conjugation, the arrow points to the _______.

sex pilus

Point mutations that change the nucleotide sequence of a codon but do not change the amino acid encoded by that codon are called ________ mutations

silent

Since the second amino acid is threonine (thr) in both the original and mutant sequences, the type of mutation illustrated here is a(n) ____ mutation

silent

A mutation that caused the codon CGU to change to CGC, which does not affect the amino acid encoded, could be described by which two of these terms?

silent, point

Select the best definition of mobile genetic elements.

specific DNA segments that can repeatedly insert into one or more sites or into one or more genomes

Mutations that result from head-on collisions between the replisome and RNA polymerase are considered to be ______ mutations

spontaneous

Mutations that result from head-on collisions between the replisome and RNA polymerase are considered to be ______ mutations.

spontaneous

Some instances of antibiotic resistance result in modification of the antibiotic target such that it is no longer inhibited by the antibiotic. Such events generally result from

spontaneous chromosomal mutations

ome instances of antibiotic resistance result in modification of the antibiotic target such that it is no longer inhibited by the antibiotic. Such events generally result from ______.

spontaneous chromosomal mutations

Which two of these missense mutations would be predicted to have the most severe effects on the function of the protein encoded by the mutated gene?

substitution of an amino acid located at the active site of an enzyme replacement of a nonpolar amino acid with a polar amino acid

A second mutation that occurs at a different site from the first mutation, and which returns the mutant back to the wild-type phenotype, is a(n) _____ mutation

suppressor

A bacteriophage that can insert its genome into a bacterial chromosome is known as a(n) _________ bacteriophage.

temperate

Mismatched DNA bases in the double helix are repaired by ________.

the mismatch repair system that eliminates the daughter strand and re-synthesizes it on the parental strand template

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

In bacterial genetics, transformation is _______.

the uptake of free DNA by a bacterial cell

Order these steps in simple transposition, with the first event at the top.

- Transposase excises the mobile genetic element - Transposase identifies a new insertion site and cleaves the strands 5 to 0 bases apart - Transposase ligates the mobile genetic element DNA with the host insertion site - Host enzymes fill in gaps, resulting in a 5 to 9 base duplication at either end of the mobile genetic element

Which three of the following are correct descriptions of plasmids?

1) They can exist independently of host chomosomes.2) Some can integrate into host chromosomes.3) They are small, double-stranded DNA molecules.

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

Which three statements apply to an F' plasmid?

An F' plasmid has been excised from a bacterial chromosome. An F' plasmid includes some chromosomal genes. An F' plasmid is an erroneously excised plasmid.

Frameshift mutation

Changes the DNA sequence by inserting or deleting a few bases to generate a polypeptide from the wrong reading frame

Missense mutation

Changes the DNA sequence to a codon that specifies a different amino acid from wild type

Silent mutation

Changes the DNA sequence to a codon that specifies the same amino acid as wild type

Nonsense mutation

Changes the DNA sequence to a stop codon to generate a shorter polypeptide

Although mismatch DNA repair and nucleotide excision repair address different types of lesions, they share three enzymes, _________, _______, and _________.

DNA polymerase I DNA ligase UvrD helicase

Which three of these statements about nonsense mutations are correct?

Effects range from mild to complete loss of normal gene function. By definition, they always produce stop codons. They cause the early termination of translation.

Which three of these statements about nonsense mutations are correct?

Effects range from mild to complete loss of normal gene function.They cause the early termination of translation.By definition, they always produce stop codons.

Which of these is the defining characteristic of an Hfr strain?

F plasmid integrated into the host chromosome

The major mechanism by which bacteria and archaea evolve (acquire novel genes) is

Horizontal gene transfer

Which two statements concerning horizontal gene transfer are correct?

Horizontal gene transfer helps microbes survive environmental stress. Horizontal gene transfer is common among microbes sharing a habitat.

Which phrase best describes the form of a gene designated the "wild type?"

The more prevalent form of the gene

Which of these descriptions applies to prototrophs?

They are chemoorganotrophs able to grow on a minimal medium containing only salts and a carbon source.

Which two of these descriptions apply to auxotrophs?

They have a conditional phenotype. They are unable to grow on medium lacking a particular molecule, where the wild-type strain could grow.

Transduction, the horizontal transfer of genes by virus particles, occurs through _________.

errors in the virus life cycle

In simple transposition, a mobile genetic element

excises from one location and inserts in a different location in the same genome

Transposases are enzymes that recognize the ends of a(n) _____.

insertion sequence

A resistance mutant may have acquired resistance to which three of the following?

pathogen antibiotic chemical

The structure used to establish physical contact between an F+ and F- cell is called a sex

pilus

Which two statements concerning horizontal gene transfer are correct?

plasmids

Silent, missense, nonsense, and frameshift are all common types of __________ mutations

point

The type of mutation that affects only a single base pair at a given DNA location is called a(n) ____ mutation

point

The genome of a temperate bacteriophage that has been inserted into a bacterial genome is called a(n)

prophage

A mutant that can survive exposure to some pathogen, chemical, or antibiotic, is a(n) ____ mutant

resistant

An allele is most likely to persist in a population if it confers a survival advantage under ______pressure.

selective

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 restores the original wild-type sequence. - A second mutation that creates a different codon that codes for the wild type amino acid.

Which two statements correctly describe missense mutations?

- Effects range from no change to complete loss of normal gene function. - They are a single base substitution that changes a codon for one amino acid into a codon for a different amino acid.

Mismatch repair Nucleotide excision repair Base excision repair

- The strand lacking methylation is removed. - matches Choice The strand with a DNA distortion is removed. - The strand with an apurinic or apyridinic site is removed.

Which two of these statements are correct about frameshift mutations?

- They usually yield mutant phenotypes. - They usually result in the synthesis of nonfunctional proteins.

By using a mutagen, the mutation rate can be increased to one mutant cell out of approximately

1,000 to 1,000,000

Under normal growth conditions, the rate of naturally-occurring mutant cells is one mutant cell out of approximately ______ cells.

10^7 to 10^11

Match each type of excision repair with the type of lesion that it repairs.

Nucleotide excision repair ----> thymine dimer Base excision repair ---> apurinic or apyrimidinic site

An F plasmid that has been excised from a bacterial chromosome, and includes some chromosomal genes, is called a(n) ______.

F' plasmid

An F plasmid that has been excised from a bacterial chromosome, and includes some chromosomal genes, is called a(n) _______.

F' plasmid

Which statement regarding viruses and their life cycles is false?

Viruses can replicate either within a host cell or autonomously.

Which of the following statements about viruses and transduction is false?

Viruses escaping a bacterium can find a new host cell and move genes to an archaeon.

Vertical gene transfer is observed in _________.

all organisms

An organism with a mutation that affects its ability to synthesize a biochemical essential for its growth is known as a(n)

auxotroph

Base analogues, DNA-modifying agents, and intercalating agents are three types of ____ mutagens

chemical

Mutations that are expressed only under certain environmental conditions are called _____ mutations

conditional

The image shows horizontal transfer of bacterial DNA by the process known as _______.

conjugation

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

distortions in the double helix thymine dimers

In mismatch repair, the DNA strand to be removed is targeted because it __________.

does not have the parental methylation pattern

DNA proofreading occurs

during DNA replication, before the next nucleotide is added

Select three examples of chemical mutagens.

intercalating agents, base analogs, DNA-modifying agents

In a genetic selection, the wild type organisms are _____, whereas in a genetic screen, the wild type organisms are ______.

killed / alive

A bacterium that has been infected by a temperate bacteriophage, and is therefore carrying a prophage, is known as a(n)

lysogen

A bacterium that has been infected by a temperate bacteriophage, and is therefore carrying a prophage, is known as a(n) _______.

lysogen

Bacteriophages that lyse their host cells after completing one cycle of replication and assembly are called

lytic

Considering the change in amino acid, the mutation illustrated in these sequences is a(n) ______ mutation

missense

Point mutations in a single base that result in a change to the amino acid encoded are called ________ mutations

missense

Select three synonyms for genetic elements that can move around genomes by transposition.

mobile genetic elements transposable elements jumping genes

Possible causes of spontaneous mutation include

mobile genetic elements, spontaneous lesions in DNA, errors in DNA replication

Transition mutations, which result in purine for purine substitution or pyrimidine for pyrimidine substitution, are ______ common than transversion mutations.

more

Silent mutations have no change in phenotype because

more than one codon exists for most amino acids

Silent mutations have no change in phenotype because _______.

more than one codon exists for most amino acids

The T4 phage of E. coli is a virulent bacteriophage, meaning that it _______.

multiplies in and lyses its host after infection

The general term for heritable changes in DNA sequence is________

mutation

A missense mutation that has little to no effect on the activity of a gene product is called a(n) ______ mutation

neutral

A tautomeric form is an isomer of a nucleotide in which the ________ is changed

nitrogenous base

Point mutations that create a stop codon within a reading frame are called ______ mutations

nonsense

Point mutations that create a stop codon within a reading frame are called _______ mutations

nonsense

Nucleotide substitutions that result in purine for purine or pyrimidine for pyrimidine mutations are known as ___________ mutations.

transition

The movement of a mobile genetic element is called

transposition

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

unmethlyated

This diagram illustrates binary fission, a type of

vertical