microbio exam 2

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The genotype of bacteria can change through either

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184 Terms

1

The genotype of bacteria can change through either

mutation or horizontal gene transfer.

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2

Bacteria are _______, so any changes in DNA can easily alter the ________.

haploid

phenotype

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A mutant that requires a growth factor ;

auxotroph;

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4

in contrast, a _______ does not require growth factors.

prototroph

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Spontaneous mutations

occur as a result of normal cell processes.

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are stable but occasionally revert back to the non-mutant form.

Spontaneous mutations

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7

The chance that two given spontaneous mutations will occur within the same cell is the
product of

the individual mutation rates

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8

Base substitutions occur during ____________

DNA synthesis

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9

_____result in synonymous, missense, and nonsense mutations

Base substitutions

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frameshift mutation

Deleting or adding one or two nucleotides

,changing the reading frame of the encoded protein.

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________results in a shortened non-functional protein.

frameshift mutation

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Transposons

can move from one location to another in a cell’s genome.

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The gene into which the transposon jumps is

insertionally inactivated by the event

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14

Induced mutations

are caused by mutagen

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15

Some chemicals modify nucleobases, altering their

hydrogen-bonding propertie

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Base analogs can be mistakenly incorporated in place of the usual _______, and they have different hydrogen-bonding properties.

nucleobases

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17

Intercalating agents insert between

adjacent bases in the double helix and push nucleotides apart,
resulting in frameshift mutations

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18

Transposons can be introduced intentionally into a cell in order to

inactivate genes.

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19

thymine dimer formation cause by

Exposure to ultraviolet light

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20

The repair mechanism can cause mutations.

thymine dimer formation

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21

X rays cause

single- and double-strand breaks

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22

Repair of Errors in Nucleotide Incorporation
DNA polymerases have a.

proofreading function.

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Mismatch repair

removes a portion of the strand that has a
misincorporated nucleotide.

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24

As a result of Mismatch repair

A new DNA strand is then synthesized

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25

Base excision repair

uses specific DNA glycosylases to remove damaged nucleobases in DNA

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photoreactivation

an enzyme uses the energy of light to break the bonds of the thymine dimer.

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In nucleotide excision repair

the damaged single-stranded segment is removed and replaced.

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28

SOS repair

is a last-effort repair mechanism that uses a special DNA polymerase that has no proofreading
ability but can bypass the damaged DNA.

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29

SOS repair results in DNA that

has many mutations

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30

Genes can be transferred by

bacterial transformation, transduction, and conjugatio

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31

For newly acquired DNA to replicate in a cell, it must either be a

replicon or integrate into the cell’s genome

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32

Bacterial transformation

transfers “naked” DNA

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33

A cell must be competent to

take up DNA, and only certain species naturally become competent.

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The Process of Natural Transformation:
Short strands of double-stranded DNA

bind to cells, but only one strand enters

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Transduction.

is the transfer of bacterial DNA by a bacteriophage

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Two types of Transduction

generalized transduction and specialized transduction

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Conjugation requires

cell-to-cell contact

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38

___ cells synthesize an____,

F+

F pilus

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39

F pilus encoded on an

F plasmid

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40

the F plasmid is transferred from an ______ to an _____

F+ cel

F− cell.

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41

Hfr cells have the ______ integrated into the chromosome.

F plasmid

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42

When the F plasmid is transferred, __________ moves into a recipient cell along with it.

chromosomal DNA

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43

An F′ donor carries

a modified F plasmid

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44

An F′ donor carries a modified F plasmid that contains

piece of chromosomal DNA

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45

pan-genome.

The sum total of genes encoded by the various strains of a given species is the

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46

What make up the core genome

Genes common to all strains of the species

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47

What are significant contributors to genome variability

Mobile genetic elements (MGEs), including plasmids, transposons, genomic islands, and phage DNA,

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48

Restriction-modification systems


allow bacterial cells to quickly distinguish and destroy invading DNA.

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49

Restriction enzymes ;

recognize and cut specific DNA sequence

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50

modification enzymes

protect the hosts’ DNA from the action of the restriction enzymes by adding methyl groups to certain nucleobases.

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51

CRISPR systems .

allow bacterial cells to destroy invading DNA that has been encountered previously

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52

CRISPR array contains

; processing of the transcript generates RNA fragments that bind to a Cas nuclease, allowing it to recognize and
destroy that DNA

The cell transcribes a chromosomal region

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53

CRISPR array contains

contains fragments captured from invading DNA;

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54

The cell transcribes a chromosomal region called a CRISPR array that contains fragments captured from invading DNA;processing of the transcript generates

DNA fragments that bind to a Cas nuclease, allowing it to recognize and
destroy that DNA.

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55

Most viruses are approximately

100-fold to 1,000-fold smaller than the cells they infect

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56

Virion (viral particle) .

consists of nucleic acid surrounded by a protein capsid

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57

Capsids are composed of .

capsomeres

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58

Some viruses have an envelope surrounding the ________; other viruses are non-
enveloped or naked. Viruses contain either RNA or DNA, but never both. The shape of a virus is generally
icosahedral, helical, or complex

nucleocapsid

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59

Viruses contain either

RNA or DNA, but never both.

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60

The shape of a virus is generally

icosahedral, helical, or complex

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61

Viruses are classified primarily

on the basis of their genome structure and hosts they infect.

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62

The names of virus families end in _____.

-viridae

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63

Viruses are also given informal names and are sometimes grouped based on their

routes of transmission.

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64

Lytic or virulent phages exit

the host at the end of the cycle by lysing the host, resulting in a productive
infection.

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65

Lytic or virulent phages exit the host at the end of the cycle by lysing the host resulting in

productive infection

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66

The infection proceeds through five steps

attachment, genome entry, synthesis of phage proteins and
genome, assembly (maturation), and release.

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67

Temperate phages have the option of either

directing a productive infection or initiating a lysogenic infection(lysogen)

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68

A repressor

.

maintains the prophage in an integrated state, but the prophage can
be excised to initiate a lytic infection.

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Lysogens are immune to

superinfection

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Lysogenic conversion occurs if

a prophage carries genes that change the phenotype of the host cell

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71

Filamentous phages cause ,

productive infections

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72

Generalized transduction results from .

a packaging error during phage assembly

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73

Generalized transducting particles can

transfer any gene of a donor cell to a recipient cell

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74

Specialized transduction results from

.

an excision mistake made by a temperate phage during its transition from a lysogenic cycle to a lytic cycle

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75

Only genes located near the site at which the temperate phage integrates are

transduced

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76

The generalized infection cycle of animal viruses can be viewed as a five-step process

Attachment
Entry and Uncoating

Synthesis of Viral Proteins and Replication of the Genome
Asse
mbly (Maturation)
Release

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Attachment

Attachment proteins or spikes on the viral particle attach to specific receptors on the cell surface.

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Entry and Uncoating: Enveloped viruses

fuse with the host membrane or are taken in by receptor-mediated endocytosis.

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Entry and Uncoating - animal viruses

the entire virion enters the cell.

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Entry and Uncoating: Non-enveloped

Non-enveloped virions enter by receptor-mediated endocytosis.

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Entry and Uncoating

releases the nucleic acid from the protein coat

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82

Synthesis of Viral Proteins and Replication of the Genome

DNA viruses generally replicate in _______ and use the _____________ as well as
_________, although they often encode their own DNA polymerase.

the nucleus

host cell machinery for DNA synthesis

gene expression

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83

Synthesis of Viral Proteins and Replication of the Genome

Replication requires a _______________ to ____________________. This enzyme lacks ___________ and makes more mistakes in replication than DNA polymerases do.

virally encoded replicase
synthesize the complementary RNA strand.

proofreading ability

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84

Synthesis of Viral Proteins and Replication of the Genome

Reverse-transcribing viruses encode _________, which
synthesizes _____________. As with replicases, these enzymes are ________.

reverse transcriptase

DNA from an RNA template

error prone

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85

Assembly (Maturation)

_______are formed, and then the genome and any necessary proteins are packaged within it.

The process may take place in the _______, ___________, ___________

Capsids

cytoplasm, in the nucleus, or in a variety of organelles

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86

Release
Enveloped virions most often exit by ________. Non-enveloped virions are released when _________

budding

the host cell dies

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87

Acute infections are characterized by

the sudden onset of symptoms of relatively short duration.

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88

Persistent infections can

continue for the lifetime of the host, with or without symptoms

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Acute Infections

On a cellular level, acute infections can be compared to _________________, but even
though the cells often die, the host may survive because of ____________

productive lytic infections by bacteriophages

the immune response

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90

Chronic infections are characterized by the

continuous production of low levels of viral particles

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91

latent infections are similar to lysogeny in bacteriophages in that the virus genome

remains in the host cell but is not active, so no new virus particles are formed

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92

Oncoviruses

are viruses that can cause cancer

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93

Oncoviruses carry ________ that interfere with the
___________________

oncogenes

ability of the cell to control growth.

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94

Most virus-induced tumors are caused by .

certain DNA viruses

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95

A vaccine against human papillomaviruses (HPVs) prevents

many cervical cancers.

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96

Oncolytic viruses target and destroy

cancer cells and have significant therapeutic potential.

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97

Catabolism

is the set of processes that capture and store energy by breaking down complex
molecules.

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98

Anabolism includes processes that

use energy to make and assemble the building blocks of a cell

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99

Photosynthetic organisms harvest the

energy of sunligh

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100

Photosynthetic organisms harvest the energy of sunlight, using it to

power the synthesis of organic compounds.

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