Microbial Genetics

Front 1

Gene Transcription

Back 1

Genes selectively transcribed to generate necessary gene products.

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Operon

Back 2

Set of genes under unified control.

Front 3

Operon Function

Back 3

Toxin production, sporulation, efflux pumps and antimicrobials, biofilm formation and quorum sensing.

Front 4

Inducible Operons

Back 4

Normally "off." Presence of substrate turns "on." Occurs during catabolic processes.

Front 5

Lac Operon Components

Back 5

Regulator (codes for repressor protein), control locus (promoter binding site for RNA polym / operator for repressor protein), structural locus, terminator (indicates end of operon).

Front 6

Lac Structural Genes

Back 6

lacZ, lacY, and lacA - coded in that order.

Front 7

lacZ

Back 7

Codes for beta-galactosidase to catabolize lactose into galactose and glucose.

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lacY

Back 8

Codes for beta-galactoside permease to import lactose through the cell membrane protein pump.

Front 9

lacA

Back 9

Codes for beta-galactoside transacetylase to transfer acetyl groups (insignificant in lactose catabolism).

Front 10

When Lactose is Absent

Back 10

Repressor protein produced, binds to operator and blocks polymerase from passing to structural genes.

Front 11

When Lactose is Present

Back 11

Lactose binds to repressor protein, inhibiting it from binding to operator. Polymerase binds to promoter and accesses structural genes. Enzymes produced and lactose catabolized.

Front 12

Repressible Operons

Back 12

Normally "on." Presence of product turns "off." Occurs during anabolic processes.

Front 13

When Alanine is Absent

Back 13

Repressor protein cannot bind to operator w/o alanine product. Polymerase binds to promotor and accesses structural genes to produce alanine.

Front 14

When Alanine is Present

Back 14

Alanine binds to repressor protein (as a corepressor) and changes its shape. Repressor binds to operator & blocks polymerase from passing to structural genes.

Front 15

Drugs that Interrupt Transcription

Back 15

Interfere by binding to polymerase.

Front 16

Drugs that Interrupt Translation

Back 16

Erythromycin, streptomycin, and tetracycline.

Front 17

Erythromycin

Back 17

Binds to 50S subunit of bacterial ribosome to prevent proteins from detaching.

Front 18

Streptomycin

Back 18

Binds to 30S subunit of bacterial ribosome resulting in misread mRNA that has trouble initially binding.

Front 19

Tetracycline

Back 19

Prevents tRNA from docking with ribosome (proteins cannot elongate).

Front 20

Microbial Evolution

Back 20

Adapts to evade host immune responses, expand into new environments, or reproduce more efficiently.

Front 21

Influenza Peplomers

Back 21

Hemagluttinin allows for host cell docking / neuraminidase keeps viruses from sticking together. Different combos for different species.

Front 22

Antigenic Drift

Back 22

Frequent, minor changes in H and N can allow for reinfection and cause local epidemics.

Front 23

Antigenic Shift

Back 23

Rare, major changes in H and N due to recombination create a new subtype and cause global pandemics.

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Mutations

Back 24

Random changes in gene sequence found in ALL pathogens. Original sequence called wild type v. mutant type. Beneficial or deleterious. If unrepaired, will be inherited by next generation.

Front 25

Mutation Categories

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Spontaneous v. induced (chemically or physically). Single (point mutation) v. multiple base pairs. Substitution (bp replaced) v. frameshift (bp lost or gained).

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Genetic Code

Back 26

Nucleic acid read in codons (groups of 3 amino acids); each codes for an amino acid. Identity and order of amino acids determines protein's shape, function, and identity.

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Substitution Mutations

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Silent: bp changes, but product does not. Missense: bp changes & product also changes. Nonsense: bp changes & results in a "stop" codon. Back: bp changes back to original form.

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Frameshift Mutations

Back 28

Shift reading frame. Insertions or deletions ("indels") that are not multiples of 3.

Front 29

Organism Mutation Repairs

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General proofreading machinery during replication: base excision repair, nucleotide excision repair, mismatch repair; glycosylase, polymerase, & ligase enzymes.

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Base Excision Repair

Back 30

Removes one wrong base.

Front 31

Nucleotide Excision Repair

Back 31

Removes stretch of bases, even if only one is wrong.

Front 32

Mismatch Repair

Back 32

Fixes bad bonding.

Front 33

DNA Photolyase

Back 33

Recognizes and repairs abnormal bonds due to UV damage.

Front 34

Virus Mutation Repairs

Back 34

DNA classes 1 and 2 utilize host cell repair mechanisms. RNA classes 3-5 and DNA class 6 have no proofreading polymerase, and thus have more errors and evolve more rapidly.

Front 35

Recombination

Back 35

Swapping of genetic material; utilized by ALL pathogens in different ways.

Front 36

Recombinant "Organisms"

Back 36

Any entity that contains & expresses genes from a different entity. Tech. genetic engineering and gene therapy.

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Prokaryotic Recombination

Back 37

Plasmids, choromosomal genes, or chromosomal fragments exchanged thru conjugation, transformation, or transduction.

Front 38

Conjugation Bacterial Factors

Back 38

Fertility (F) factor on plasmids. High-frequency (Hfr) factors integrated into bacterial genomic material.

Front 39

Conjugation Process

Back 39

Sex pilus emerges from F+ or HFr bacterium, docks with recipient, retracts to draw the two together, conjugation bridge forms, material exchanged.

Front 40

Transformation

Back 40

Exchange of chromosomal fragments from lysed cells. DNA-binding proteins on bacterial cell walls facilitate uptake. Rare physical contact.

Front 41

Griffith's Experiment

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Smooth virulent and rough nonvirulent bacteria combination transformed R into S.

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Transduction

Back 42

Exchange of genes facilitated by viruses. Generalized or specialized.

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Generalized Transduction

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Virus infects cell & host DNA disassociates during hijacking; host DNA incorporated into virus during virion assembly; cell lyses and virions released; virus transfers bacterial DNA to new host.

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Specialized Transduction

Back 44

Prophage enters lytic cycle; as it excises from host genome it grabs part of bacterial genome; replicates; infects new cell and integrates bacterial genes.

Front 45

Lysogenic Conversion

Back 45

Virus changes properties of bacterial host through transduction (ex. toxins, antimicrobial resistance, gene regulatory elements)

Front 46

Recombination in Eukaryotes

Back 46

Meiosis main source of variation.

Front 47

Recombination in Viruses

Back 47

"Bacterial sex" (conjugation), transduction, recombination (polymerase strand jumping), reassortment.

Front 48

Reassortment

Back 48

Lg. pool of genetic material can assemble viruses from two segmented viruses, offering tremendous genetic diversity.