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Pathology 1 > Bacterial Genetics > Flashcards

Bacterial Genetics Flashcards

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1
Q

What is genetics?

A

The study of genomes and DNA/RNA, genome replication, gene expression, genetic variation & distribution

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2
Q

Describe the flow of genetic info when forming a protein

A

To form a protein, DNA transcribed into mRNA which is translated into a protein

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3
Q

How does replication error occur during evolution?

A

DNA polymerase can make errors

e,g, single nucleotide polymorphisms (SNPs)

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4
Q

What is a common plasmid transfer mechanism?

A

Bacterial Conjugation

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5
Q

Why is the study of bacterial genetics so significant?

A
  • bacteria cause infection & are key components of
    microbiome
  • important industrial organisms
  • small single-copy genomes that are relatively simple &
    easy to study
    –> manipulating tools for genomes originate from
    bacteria
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6
Q

What is the function of proteins?

A

Perform most cell functions including catalysis and synthesis of other structures therefore genome sequence controls all cell functions

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7
Q

How is bacterial transformation used in the lab?

A

Bacterial transformation is exploited in the lab to artificially move purified plasmids into bacteria

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8
Q

What is the significance of next generation sequencing?

A

e.g. Illumine benchtop machines
can sequence a bacterial isolate for £50 a day
- routine research laboratory
- introduction into microbiology diagnostic labs

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9
Q

Outline how plasmid transfer occurs

A
  1. Donor cells attaches to recipient cell via pillus which
    draws cells together
  2. Cells contact one another
  3. One of strand of plasmid DNA transfers to recipient
  4. The recipient synthesises a complementary strand to
    become F+ cell
    - the donor synthesises a complementary strand, restoring its complete plasmid
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10
Q

What are MGEs?

A

Mobile gene element that move around within genomes

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11
Q

How is the genome used in the lab?

A

New technologies leads to new understanding
whole genome sequencing + new computing power
Haemophillus influenza was the first bacterial genome sequenced

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12
Q

What is the significance of prophages?

A

The prophage can encode important virulence genes
e.g. cholera, diphtheria, botulism toxins & panton-
valentine leukocidin

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13
Q

What is CRISPR?

A

Clustered Regularly Interspaced Short Palindromic Repeats

- in 40% of bacteria

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14
Q

How does bacterial genome replication occur?

A

Replication is the first step in bacterial cell division
DNA polymerase catalyses the reaction to synthesise new genome
Requires primers and DNA template strand

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15
Q

How is genetic manipulation of eukaryotes carried out?

A

CRISPR is the most exciting new technology for eukaryotic cells gene editing and is a potential for treating genetic disorders e.g CF

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16
Q

What are bacteriophages?

A

MGE Viruses of bacteria

  • can lyse & kill bacteria
  • or genome sits in bacterial chromosomes (prophage)
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17
Q

What is the significance of bacterial gene regulation?

A

Bacteria are single celled organisms that are highly responsive to environmental triggers
e.g.
- nutrients, Oxygen, Iron
- Temperature, Bacterial pheromones, Mammalian cells &
hormones

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18
Q

Describe the bacterial genome

A

All DNA in a bacterial cell includes

  • chromosomes - circular, single copy
  • plasmids - autonomously replicating circular DNA
  • prophage - viruses integrated into chromosomes
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19
Q

What is the consequence of genome replication errors?

Study These Flashcards
A

Some errors can be fixed but errors can be accumulated

Errors can be advantageous, detrimental or neutral to the bacterial cell in a particular habitat

20
Q

What is the significance of MGEs?

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A

Horizontal transfer of MGEs
Many MGEs encode virulence, antimicrobial resistance or host specific genes.
Acquisition of MGEs leads to new bacterial variants with enhanced virulence or resistance in their host ranges

21
Q

Describe the MRSA strain genome

Study These Flashcards
A

2.9m base pairs in chromosomes
carries integrated prophage, transposons, pathogenicity islands and antimicrobial resistance elements
Encodes roughly 2800 genes

22
Q

Outline how knockout is constructed

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A
  1. Clone virulence gene into ‘suicide vector’ plasmid
  2. Clone antibiotic resistance marker into gene to disrupt
    it
  3. Transform it into bacterial cell
  4. Recombination via RecA (rare)
  5. Place onto agar with antibiotic and select for rare
    isolate that has resistance marker
23
Q

When are bacterial virulence factors expressed?

Study These Flashcards
A

Many bacterial virulence factors are only expressed in vivo or in conditions mimicking in vivo

24
Q

What does the genome determine?

Study These Flashcards
A

Bacterial capabilities - can predict function by identifying patterns homology of known genes & motifs

25
What is the significance of studying bacterial gene functions?
Genes are necessary for phenotype and pathogenesis especially for complex virulence pathways involving more than one gene
26
Why are bacterial genomes manipulated?
To make tools for industrial production of proteins | To make tools for studying bacteria / gene function
27
Can all DNA be transferred into bacteria?
No not all DNA can be transferred into bacteria as Bacterial immunity protects itself from foreign DNA
28
Give examples of bacterial virulence factors being selectively expressed in vivo
Vibrio cholera expresses cholera toxin and pilin necessary for colonisation only in human intestinal tract Corynebacterium diphtheriae only produces diphtheriae toxin in low iron conditions e.g. in vivo
29
Describe how gene expression is regulated via the Lac Operon
1. Absence of lactose - lac repressor binds to operator, blocking transcription 2. Presence of lactose - lactose binds to lac repressor, releasing it from operator, allowing RNA Pol. to proceed with transcription at a slow rate - cAMP and CAP complex increases RNA pol. activity - but have no effect in lactose absence
30
What is general transduction?
Temperate bacteriophages 'accidentally' packages host bacterial DNA or plasmids into phage particles and delivers it to new bacteria
31
What is the significance of RNA sequencing & transcriptional circuits?
Only genes important for survival & virulence are expressed Gene regulation pathways that respond to in vivo signals are targets for therapeutics
32
How does restriction modification occur?
SRM molecule binds to DNA R (restriction) digests M (modification) methylates and protects DNA
33
What is the consequence of the bacteriophage mechanism?
1. Genes encoded on phage begin forming proteins 2. Proteins formed assemble structures into phage particles 3. Phage particles formed suck up phage genome copies into heads 4. Bacteria killed and phage is released 5. Phage particles find a new host's outside to latch onto & infect DNA into new bacterial cell That DNA can now circuarise and integrate into chromosomes
34
When is isogenic mutant pairs / knockouts used?
Used to study bacterial / gene function
35
Give examples of homologous regions in bacterial genomes
Putative genes - encode proteins with predicted functions - toxins, virulence factors, metabolic pathways Gene regions with predicted functional regions - transmembrane regions, ATP binding region - start & stop codons - RNA pol gene regulatory binding site - Integrated mobile genetic elements
36
What are Plasmids?
Type of MGE that replicate autonomously and have circular DNA Aren't essential for host Bacteria
37
How do MGEs move between bacteria?
Bacterial Transformation - release of DNA and antibiotic resistant gene into recipient cell Bacterial Transduction - Release of phage from a phage-infected donor cell into recipient cell Bacterial conjugation - Transposin plasmid from donor cell into recipient cell
38
What are the different sites present on plasmids?
- Origin of replication - Antibiotic resistant gene - selectable marker - promoter - 5' primer site - restriction sites - inserted gene - 3' primer site
39
Outline how RNA sequencing is done in a lab
1. Grow bacteria in conditions of interest 2. Extract bacteria (extract bacterial mRNA & convert to DNA) 3. Sequence DNA and quantitate numbers of each genes transcript
40
What is a gene?
Hereditary protein / DNA template / base sequence with potential to be translated into a specific protein
41
Outline the bacteriophage mechanism
Induced by stress (UV light infection) 1. Phage genome pops out of chromosome & circularises 2. Circular phage pops back in chromosome 3. Replicates & makes many more copies => lysogenic phase
42
Which bacteria are plasmids used as cloning vectors for?
E. coli ampR E. coli ori LacZ
43
Outline the key features of DNA
- double helix of polynucleotide - DNA sequence composed of 4 nucleotide bases A,T,G,C - form complementary base pairs via hydrogen bonds AT and GC
44
Give an example of how genomes are manipulated
Cloning genes - transfer of insulin genes via recombinant plasmid 1. Digest plasmid with restriction enzyme 2. Use same restriction enzyme to cut DNA strands ==> forms sticky ends 3. Seal gap with ligase enzyme
45
Which region on the plasmid is highly targeted by multiple restriction enzymes?
The cloning region

Pathology 1 (20 decks)

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