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Microbial Genetics and Metabolism > Microbial Genetics > Flashcards

Microbial Genetics Flashcards

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1
Q
  • basic unit of heredity
  • segments of DNA (RNA for some
    viruses) that code for functional
    products (proteins, RNAs)
  • DNA sequences that are required to
    produce a polypeptide chain
A

Gene

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2
Q
  • regions of DNA that contain the actual
    instructions for the sequence of amino
    acids in a protein (coding regions)
  • stretches of DNA sequence that help
    regulate expression of gene (noncoding
    regions)
A

Polypeptide chain

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3
Q

macromolecule composed of repeating units called nucleotides

A

DNA

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4
Q

nitrogenous base + deoxyribose + phosphate group ( the 3 components)

A

Nucleotide

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5
Q
  • string of nucleotides
    joined together by
    phosphodiester linkages
  • macromolecule
  • deoxyribonucleoside 5-
    monophosphate
A

Molecular Structure of DNA: Primary Structure

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6
Q
  • three-dimensional
    configuration of DNA
  • double helical structure
  • two polynucleotide
    strands wound around
    each other
A

Molecular Structure of DNA: Secondary Structure

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7
Q

DNA Model: two long polynucleotide chains are coiled around a central
axis, forming a right-handed _____________

A

double helix

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8
Q

Two chains of DNA Model are _____________

A

antiparallel (C-5’-to-C-3’ orientation runs in opposite directions)

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9
Q

base of both chains are paired to one another as the result of the formation of hydrogen bonds

A

specificity and complementarity (A=T, C=G)

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10
Q

Molecular forces that hold two strands together:

A

▪ Hydrogen bond
▪ hydrophobic interactions between stacked base pairs

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11
Q

▪ found in cytoplasm
▪ circular chromosome
▪ single chromosome plus plasmid
▪ made up of only DNA
▪ copies its chromosomes and divides immediately

A

Prokaryotic Chromosome

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12
Q

▪ found in nucleus
▪ linear chromosome
▪ many chromosomes, usually 10-50 chromosomes in somatic cells
▪ made up of DNA, histone proteins
▪ copies its chromosome grows cell and then divides equally through mitosis

A

Eukaryotic Chromosome

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13
Q

Bacteria have a ___________________ consisting of a single circular molecule of DNA with associated proteins

A

single circular chromosome

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14
Q

The chromosome is _________________________ and attached at one or several points to the plasma membrane.

A

Looped and folded

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15
Q

The chromosome takes up only about 10% of the cell’s volume because the ________________

A

DNA is twisted, or supercoiled

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16
Q

Model of E. coli Chromosome

A

Folded = coiled
Nicked = single strand

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17
Q

Chromosome length of E.coli

A

~1 mm

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18
Q

individual unit of replication

A

replicon

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19
Q

where replication starts and continues until entire replicon has been replicated

A

origin of replication

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20
Q

loop where replication occurs

A

replication bubble

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21
Q

point of unwinding, where two single nucleotide
strands separate from the double-stranded DNA helix

A

replication fork

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22
Q

DNA Replication Takes Place in a
_________________ Manner

A

Semiconservative

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23
Q

❑ intragenic regions
❑ intervening
nucleotide
sequences that do
not directly code for
proteins and are
removed in pre-mRNA

A

Introns

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24
Q

portions of gene that codes for amino acids

A

Exons

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25
Q

Three staged of Prokaryotic Translation

A

Initiation, Elongation, Termination

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26
Q

binding of ribosome (containing rRNAs and proteins) and aminoacyl tRNA to mRNA.

A

Initiation

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27
Q

addition of one aa at a time to the growing polypeptide chain

A

Elongation

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28
Q

release of finished polypeptide from tRNA and dissociation of ribosome from mRNA

A

Termination

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29
Q

determines how the nucleotide sequence specifies the amino acid
sequence of a protein

A

Genetic code

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30
Q

three nucleotides encode each amino acid in a protein

A

triplet code

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31
Q

❑ basic unit of the genetic code
❑ set of bases that encode a single amino acid
❑ contains three nucleotides

A

codon

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32
Q

three stop codons:

A

UAA, UAG, UGA

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33
Q

is written in a linear form, using the ribonucleotide bases that compose mRNA molecules as “letters”

A

Genetic code

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34
Q

is derived from the complementary nucleotide bases in DNA.

A

Ribonucleotide sequence

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35
Q

prokaryotic mRNA can be _____________

A

polycistronic

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36
Q

can produce more than one protein

A

polycistronic

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37
Q

eukaryotic mRNA are usually _________________

A

monocistronic

38
Q

each can encode only a single polypeptide

A

monocistronic

39
Q

Pre Transcriptional Controls

A

Repression and Induction

40
Q

❑ Two genetic control mechanisms that regulate the transcription of mRNA, and consequently, the synthesis of enzymes from them.
❑ These mechanisms control the formation and amounts of enzymes in the cell, not the activities of the enzymes.

A

Repression and Induction

41
Q

The regulatory mechanism that inhibits gene expression and decreases the synthesis of enzymes.

A

Repression

42
Q

the process that turns on the transcription of a gene or genes

A

Induction

43
Q

a substance that initiates transcription of a gene

A

Inducer

44
Q

enzymes that are synthesized in the presence of inducers

A

Inducible enzymes

45
Q

Example of an inducible system:

A

genes required for lactose metabolism in E. coli

46
Q

True or False: The default position of a repressible gene is off.

A

False: on

47
Q

True or False: The default position of an inducible gene is on.

A

False: off

48
Q

the bacterial cells can produce a large quantity of the enzyme when ______________ is added to the medium

A

lactose

49
Q

the presence of ___________ indirectly induces the cells to synthesize more enzyme

A

lactose

50
Q

Pre-Transcriptional Controls

A

Positive and Negative controls

51
Q

❑ processes that stimulate gene expression
❑ regulatory protein is an activator

A

Positive control

52
Q

❑ processes that inhibit gene expression
❑ regulatory protein is a repressor

A

Negative control

53
Q

Formulated the operon control of gene expression by induction and repression:

A

Francois Jacob and Jacques Monod (1960s)

54
Q

The model shows induction of the enzymes of lactose catabolism in E. coli

A

Operon model

55
Q

❑ bacterial genes that have related functions are clustered together
❑ bacterial genes that have related functions are under the control of a
single promoter
❑ often transcribed together into a single mRNA

A

OPERON

56
Q

❑ group of bacterial structural genes that are transcribed
together (with their promoter and additional sequences that
control transcription)
➢ basic unit of transcriptional control in bacteria

A

OPERON

57
Q

Two relatively short segments of DNA in lac operon:

A

Promoter, Operator

58
Q

is the segment where RNA polymerase initiates transcription

A

Promoter

59
Q

acts as a go or stop signal for transcription of the structural genes

A

Operator

60
Q

the combination of the three lac structural genes and the adjoining control regions is called _______________

A

LAC OPERON

61
Q

OPERON STRUCTURE:

A

Structural genes, Promoter, Regulator Gene, Regulator protein

62
Q

transcribed into a single mRNA, which is
translated to produce enzymes (transcription is under the control of a promoter)

A

structural genes

63
Q

where RNA polymerase binds to and moves
downstream, transcribing the structural genes

A

promoter

64
Q

helps control transcription of the structural genes
of the operon (not part of the operon, has its own promoter and is transcribed into short mRNA and translated into small protein or regulator protein)

A

regulator gene

65
Q

bind to a region of DNA operator and affect
whether transcription can take place

A

regulator protein

66
Q

The Operon Model of Gene Expression

A

LAC PERMEASE, TRANSACETYLASE, STRUCTURAL GENES

67
Q

is involved in the transport of lactose into the cell

A

LAC PERMEASE

68
Q

metabolizes certain disaccharides other than lactose

A

TRANSACETYLASE

69
Q

the genes, which determine the structures of proteins

A

STRUCTURAL GENES

70
Q

LAC Operon Enzymes:

A

Permease, β-galactosidase, Thiogalactoside transacetylase

71
Q

❑ actively transports lactose into the cell
❑ encoded by lacZ gene

A

Permease

72
Q

❑ breaks lactose into glucose and galactose; can convert lactose to allolactose (has a role in regulating lactose metabolism)
❑ encoded by lacY gene

A

β-galactosidase

73
Q

❑ unknown function
❑ encoded by lacA gene

A

thiogalactoside transacetylase

74
Q

❑ regulator gene
❑ transcribed into a short mRNA and translated into a repressor/inhibitor
❑ consist of four identical polypeptides
❑ has two binding sites
❑ one site binds to allolactose
❑ other site binds to DNA

A

lacI

75
Q

a regulatory gene that encodes a repressor protein that switches inducible and repressible operons on or off

A

I gene

76
Q

true or false: the lac operon is an inducible operon

A

True

77
Q

true or false: in the presence of lactose, the repressor binds to the operator site, thus preventing transcription

A

False: absence of lactose

78
Q

true or false: If lactose is present, the repressor binds to a metabolite of lactose instead of to the operator, and lactose-digesting enzymes are transcribed.

A

true

79
Q

❑ those in which transcription is normally off (not taking place)
❑ something must happen to induce transcription or turn it on

A

inducible operons

80
Q

❑ those in which transcription is normally on (taking place)
❑ something must happen to repress transcription or turn it off

A

repressible operons

81
Q

When excess tryptophan is present, the tryptophan acts as a ________________ binding to the repressor protein. The repressor protein can
now bind to the operator, stopping further tryptophan synthesis.

A

Corepressor

82
Q

negative repressible operon

A

TRP Operon

83
Q

negative repressible operon

A

TRP Operon

84
Q

a substance derived from ATP that serves as a cellular alarm signal.

A

cAMP

85
Q

Enzymes that metabolize glucose are constitutive, and cells grow at their maximal rate with ____________ as their carbon source because they can use it most efficiently.

A

glucose

86
Q

transcription of the lac operon requires both the presence of ___________ and the absence of _____________

A

lactose, glucose

87
Q

transcription of the lac operon requires both the presence of ___________ and the absence of _____________

A

lactose, glucose

88
Q

is an example of an alarmone, a chemical alarm signal that promotes a cell’s response to environmental or nutritional stress. (The stress is the lack of glucose)

A

Cyclic AMP

89
Q

inhibition of the metabolism of alternative carbon sources by glucose is termed

A

catabolite repression or the glucose effect

90
Q

Eukaryotic and bacterial cells can turn genes off by ______________ certain nucleotides—that is, by adding a methyl group 1-CH3 2.

A

methylating

Microbial Genetics and Metabolism (2 decks)

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