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Microbiology > Microbial Genetics > Flashcards

Microbial Genetics Flashcards

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Biology 101 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
Q

where is RNA made in eukaryotes and transported into where

A

nucleus and transported to cytoplasm

26
Q

where is DNA and ribosomes in eukaryotes

A

dna - membrane nucleus

ribosomes = outside of nucleus

27
Q

where are DNA and ribosomes in prokaryotes

A

both in the cytoplasm, occurs quickly

28
Q

where is RNA made and protein formed in prokaryotes

A

both occurs in cytoplasm

29
Q

transcription and translation in prokaryotes

A

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
Q

how are regulation of genes occurs in bacteria?

how can they express genes?

A

through transcription, translation and global regulation

31
Q

how are genes regulated in transcription?

A

Production of regulatory proteins( lactose operon)

Interruption of transcription (attenuation) = transcription regulation without the need of regulatory proteins

32
Q

how are gene regulated by global regulation

A 
Catabolite repression
Nitrogen regulation
Phosphorus regulation
Stringent response
Heat shock proteins
33
Q

what is genetic mutations

A

any change in the genomic DNA sequence of an organism

34
Q

what are the causes for dna mutations

A

chemical mutagens

physical mutagens
- UV light, radiation

biological mutagens
- transposable elements

35
Q

what types of mutations are there

A

base substitution, deletion, inversion, transposition, duplication

36
Q

what are the consequences of DNA mutations

A
  1. no effect
  2. lethal mutation
  3. conditional mutation
  4. reverse a previous mutation
37
Q

lac I

A

Inhibition

38
Q

lacY permease

A

creates a channel for diffusion to allow all the lactose outside to stream in

39
Q

what are common mutant phenotypes

A

antibiotic - resistant mutants

nutritional mutants

carbon-source mutants

40
Q

what are antibiotic- resistant mutants

A

able to grow on host containing an antibiotic

41
Q

what is nutritional mutants

A

unable to synthesise an essential nutrient

needs nutrient as a supplement for successful growth

42
Q

what are carbon-source mutants

A

unable to use a specific carbon substance as a source of energy

unable to grow on medium if substance is sole source

43
Q

what are the ways to select and identify mutants

A
  1. direct selection
  2. indirect selection
  3. site-direct mutagenesis
    4, Brute strength
44
Q

what is direct selection

A

Create conditions to favor growth of desired mutant
e.g. growth of bacteria in presence of antibiotic

Only successful growth are mutants

45
Q

what is indirect selection

A

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
Q

what is site-directed mutagenesis

A

Recombinant DNA manipulation

Selectively mutate a particular gene

47
Q

what is brute strength

A

Screen large numbers (upwards of 10,000 clones)

Replica plating (speeds up process) Transfer large numbers of colonies, track growth

48
Q

what are the three types of genetic transfer

A
  1. transformation
  2. conjugation
  3. transduction
49
Q

what is genetic transformation

A

donor DNA taken up from external environment

50
Q

what is genetic transfer conjugation

A

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
Q

what are the steps in conjugation

A

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
Q

what is transduction in genetic transfer

A

DNA transfer from 1 bacterium to another via bacteriophage lysogenic infection

see virus lecture for details on mechanism

53
Q

what are the steps in transduction

A

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
Q

brute strength negative histadine example

A

missing colony, auxotroph, can’t grow if it is missing something

e.g. negative histadine auxotroph, can’t grow without histadine

55
Q

does genetic transfer maximise genetic diversity

A

yes increases, adaptive possibilities, survival rates in extreme conditions, exploitation of new environments

Microbiology (5 decks)

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