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Microbiology > Microbial Genetics > Flashcards

Microbial Genetics Flashcards

1
Q

what is the structure of DNA

A
  • 2 strands of DNA (anti-parallel)
  • double helix
  • nucleotides
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2
Q

what are nucleotides

A
  • hydrogen bonds between strands

- neighbouring deoxyribose connected

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3
Q

what is base pairing

A

G and C (3H bonds)

A and T (2H bonds)

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4
Q

where is the DNA stored in eukaryotes

A

in the nucleus

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5
Q

where is the dna stored in prokaryotes

A

in cytoplasm

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6
Q

what is bacterial genetics

A
  • no nuclear membrane
  • single circular chromosome
  • no intronic DNA
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7
Q

what is extra chromosomal DNA

A
  • known as plasmids
  • cells have 1 or more copy of plasmids
  • replicate independently of main chromosome
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8
Q

pyrimidine

A

cytosine and tyrosine

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9
Q

purine

A

alanine and guaine 2 rings

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10
Q

what are the roles of DNA

A
  1. DNA replication

2. Gene Expression

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11
Q

what is DNA replication

A

process by which DNA double helix unwinds & makes a copy of itself

needs to be copied accurately

necessary for cell division

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12
Q

what is gene expression

A

Information stored in DNA is used to tell the cell what to do

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13
Q

dna polymerase

A

responsible for forming new copies of DNA, in the form of nucleic acid molecules

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14
Q

what is the genome

A

Total DNA of a cell

In bacteria_ most have single circular chromosome, some are linear

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15
Q

what are plasmids

A

small, circular, extra-chromosomal DNA

encode beneficial factors

resistance factors (antibiotic)

conjugative plasmids (or F factor)

F+ bacteria can pass from 1 bacteria to another

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16
Q

Genotype

A

genetic makeup/blueprint

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17
Q

phenotype

A

appearance & function

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18
Q

what types of DNA replication is there

A
  1. semi-conservative

2. replication fork

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19
Q

what is semi-conservative dna replication

A

After replication each chromosome consists of:

  • 1 old template strand
  • 1 newly synthesised strand
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20
Q

whaat is replication fork dna replication

A

multiple enzymes processing the following:

- DNA unwinds
- exposes nucleotides
- Synthesise (DNA polymerase) the new strand in one direction only = 5’ to 3’
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21
Q

horizontal gene transfer

A

is the non-sexual movement of genetic information between genome

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22
Q

what is the replication of circular bacterial chromosomes

A
  1. origin of replication (bubble forms, DNA unwinds)
  2. replication occurs in both directions
  3. continue until replication forks meet
  4. strands separate create 2 chromosomes
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23
Q

where does transcription and translation occur in eukaryotes

A

transcription = nucleus

translation = cytoplasm

24
Q

where does transcription and translation occur in prokaryotes

A

translation = cytoplasm

transcription = cytoplasm

25
where is RNA made in eukaryotes and transported into where
nucleus and transported to cytoplasm
26
where is DNA and ribosomes in eukaryotes
dna - membrane nucleus ribosomes = outside of nucleus
27
where are DNA and ribosomes in prokaryotes
both in the cytoplasm, occurs quickly
28
where is RNA made and protein formed in prokaryotes
both occurs in cytoplasm
29
transcription and translation in prokaryotes
DNA containing gene targeted for transcription mRNA chain is transcribed from DNA by (many) RNA polymerase The (many) nascent mRNA are formed translation begins with ribosomes ‘rushing’ to the (many) nascent mRNAs Of note: One single nascent mRNA can be targeted by many ribosomes at a time (polysome)
30
how are regulation of genes occurs in bacteria? how can they express genes?
through transcription, translation and global regulation
31
how are genes regulated in transcription?
Production of regulatory proteins( lactose operon) Interruption of transcription (attenuation) = transcription regulation without the need of regulatory proteins
32
how are gene regulated by global regulation
``` Catabolite repression Nitrogen regulation Phosphorus regulation Stringent response Heat shock proteins ```
33
what is genetic mutations
any change in the genomic DNA sequence of an organism
34
what are the causes for dna mutations
chemical mutagens physical mutagens - UV light, radiation biological mutagens - transposable elements
35
what types of mutations are there
base substitution, deletion, inversion, transposition, duplication
36
what are the consequences of DNA mutations
1. no effect 2. lethal mutation 3. conditional mutation 4. reverse a previous mutation
37
lac I
Inhibition
38
lacY permease
creates a channel for diffusion to allow all the lactose outside to stream in
39
what are common mutant phenotypes
antibiotic - resistant mutants nutritional mutants carbon-source mutants
40
what are antibiotic- resistant mutants
able to grow on host containing an antibiotic
41
what is nutritional mutants
unable to synthesise an essential nutrient needs nutrient as a supplement for successful growth
42
what are carbon-source mutants
unable to use a specific carbon substance as a source of energy unable to grow on medium if substance is sole source
43
what are the ways to select and identify mutants
1. direct selection 2. indirect selection 3. site-direct mutagenesis 4, Brute strength
44
what is direct selection
Create conditions to favor growth of desired mutant e.g. growth of bacteria in presence of antibiotic Only successful growth are mutants
45
what is indirect selection
Prevent growth of mutant cells Kill growing cells, non-growing (mutant cells) survive e.g. add penicillin, inhibits formation of new peptidoglycan cross links
46
what is site-directed mutagenesis
Recombinant DNA manipulation Selectively mutate a particular gene
47
what is brute strength
Screen large numbers (upwards of 10,000 clones) Replica plating (speeds up process) Transfer large numbers of colonies, track growth
48
what are the three types of genetic transfer
1. transformation 2. conjugation 3. transduction
49
what is genetic transformation
donor DNA taken up from external environment
50
what is genetic transfer conjugation
donor DNA transferred by physical contact between donor & recipient cells Temporary union of 2 bacterial cells during which 1 cell transfers a plasmid (fertility factor) to the other (via sex pilus)
51
what are the steps in conjugation
step 1: F+ and F- cells come attached by sex pillus on F+ step 2: sex pillus retracts brings cells together step 3: conjugative plasmid is nicked and replication creates a single strand DNA, which enters F- cell Step 4: DNA duplicated and forms a circular plasmid. Both cells F+
52
what is transduction in genetic transfer
DNA transfer from 1 bacterium to another via bacteriophage lysogenic infection see virus lecture for details on mechanism
53
what are the steps in transduction
step 1: phage injects it DNA step 2: phage enzymes degrade host DNA step 3: cells synthesises new phages that incorporate phage DNA and mistakenly, some host DNA step 4: transacting phage injects donor dna step 5: donor dna disincorporated into recipients chromosome by recombination
54
brute strength negative histadine example
missing colony, auxotroph, can't grow if it is missing something e.g. negative histadine auxotroph, can't grow without histadine
55
does genetic transfer maximise genetic diversity
yes increases, adaptive possibilities, survival rates in extreme conditions, exploitation of new environments

Microbiology (5 decks)

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