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bgm1004-genetics > BGM1004/L03 Bacterial Genetics II > Flashcards

BGM1004/L03 Bacterial Genetics II Flashcards

1
Q

What is the Central Dogma of Biology?

A

DNA-RNA-Protein

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2
Q

What is different about transcription and translation in bacteria?

A

They are coupled

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3
Q

Describe what coupled transcription and translation means in bacteria.

A

Ribosomes bind to RNA as it is transcribed

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4
Q

Why can’t transcription and translation be coupled in higher organisms?

A

Transcription and translation occur in different cellular compartments

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5
Q

Approximately how proportion of base pairs are organised into genes that code for proteins or (less often) RNA in bacteria?

A

95%

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6
Q

Approximately what proportion of DNA is involved in gene expression and structural organisation in bacteria?

A

5%

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7
Q

Give the 3 phases of transcription.

A

Initiation
Elongation
Termination

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8
Q

Describe initiation.

A

RNA polymerase binds to promoter sequence and starts transcription

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9
Q

Describe elongation.

A

RNA polymerase uses DNA as a template to synthesise RNA from ribonucleotide triphosphates

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10
Q

Describe termination.

A

RNA polymerase recognises sequences in RNA that stops RNA synthesis

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11
Q

Give the 3 most common types of RNA.

A

Messenger RNA
Ribosomal RNA
Transfer RNA

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12
Q

What base differs between DNA and RNA?

A

Thymine - Uracil

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13
Q

How many bases make a codon?

A

3

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14
Q

How many stop codons are there?

A

3

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15
Q

How many reading frames does each piece of duplex DNA have?

A

6

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16
Q

Where does mRNA bind on the ribosome to begin transcription?

A

End of 16S ribosomal RNA

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17
Q

What form does most bacterial DNA take?

A

Circular chromosome (plasmid)

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18
Q

What enzymes are responsible for DNA synthesis?

A

DNA-dependent DNA polymerases

19
Q

Why is DNA replication described at semi-conservative? (2)

A

One strand consists of original DNA and one newly synthesised DNA
Old strand used to correct errors in new strand

20
Q

What is required to initiate DNA synthesis?

A

Pre-existing RNA or DNA primer

21
Q

What bonds do DNA polymerases form and where?

A

Phosphodiester bonds
Between 3’OH of DNA and 5’PO4 on incoming dNTP

22
Q

What is the unique site of bacterial replication called?

A

Origin of replication (OriC)

23
Q

How does plasmid replication proceed?

A

Bi-directionally from origin to terminus (terC)

24
Q

What are the 2 sites of RNA synthesis called?

A

Replication forks

25
Q

How are mutations detectable? (2)

A

Sequence analysis or change in phenotype

26
Q

Give 4 examples of types of mutations.

A

Base-pair changes
Frameshifts
Deletions
Insertions
Inversions
Duplications

27
Q

What is a transition mutation?

A

A swap between two purines OR two pyramidines

28
Q

What is a transversion mutation?

A

A swap between a purine and a pyramidine

29
Q

Give 3 potential consequences of base-change mutations.

A

No change
One amino acid change
Premature stop codon

30
Q

What is a silent mutation?

A

A mutation having no change on amino acid sequence

31
Q

What is a nonsense mutation?

A

A mutation resulting in a premature stop codon

32
Q

What is a missense mutation?

A

A mutation having an impact on one amino acid in sequence

33
Q

What is a frameshift mutation?

A

A mutation resulting in a shift in the reading frame

34
Q

What types of mutation can cause a frameshift?

A

Insertion or deletion of several bases not divisible by 3

35
Q

What is the probability that a randomly generated codon will be a stop codon?

A

1/20

36
Q

What is the equation for mutation frequency?

A

MF = m/N
Where m= no. mutants
N = total no. bacteria

37
Q

Why do mutations occur spontaneously at low frequencies?

A

Powerful repair mechanisms

38
Q

What needs to occur to increase mutation frequency?

A

Overloading of repair systems

39
Q

How can bacterial repair systems be overloaded?

A

Treatment with chemicals/radiation to damage DNA

40
Q

Describe general selection of mutants.

A

Isolate randomly distributed mutants
Screen for desired mutant

41
Q

Describe specific selection of mutants.

A

Every mutant isolated is of interest
Requires knowledge of system

42
Q

Describe negative selection of mutants.

A

Select against mutant growing

43
Q

Describe enrichment selection of mutants.

A

Inhibit growth of mutants and kill wildtype using antibiotics

44
Q

Describe positive selection of mutants.

A

Selective conditions where only mutants grow

bgm1004-genetics (22 decks)

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