Microbiology Block B Lecture 3

Front 1

What are the classical approaches to ascribing gene function

Back 1

Describe phenotype of mutant

Genetic analysis to identify location of gene

Analysis of gene

Cloning of genes

Sequencing of genes

Front 2

What is a mutation

Back 2

Heritable change in DNA sequence that can lead to a change in phenotype

Front 3

What is a mutant

Back 3

A statin of an cell or virus differing from parental strain in genotype

Front 4

What is a wild type strain

Back 4

Typically refers to strain isolate from nature

Front 5

What is a selectable mutation

Back 5

Give the mutant brother advantage under certain conditions

Front 6

What are non selectable mutations

Back 6

No advantage or disadvantage

Front 7

How do you delete a non selectable mutation

Back 7

Examine a large number of colonies and looking for difference (screening)

Front 8

What are induced mutations

Back 8

Made environmentally or deliberately can result from exposure to natural radiation or oxygen radicals

Front 9

What are spontaneous mutations

Back 9

Occurs without external intervention

Front 10

What are point mutations

Back 10

Mutations that only change one base pair can lease to single amino acid change in a protein an incomplete protein

Front 11

What is a silent mutation

Back 11

Doesn’t affect amino acid sequence

Front 12

What is a missense mutation

Back 12

Amino acid Ed change. Polypeptide altered

Front 13

What is a nonsense mutation

Back 13

Codon becomes stop codon polypeptide is incomplete

Front 14

What is a frameshift mutation

Back 14

Deletions or insertions that result in a shift in the reading frame. Often result in complete loss of gene function

Front 15

Are point mutations reversible

Back 15

Typically yes

Front 16

What is a reversion mutation

Back 16

Alteration in DNA that reverses the effects of a prior mutation

Front 17

What do a reverent mutation

Back 17

Strain in which original phenotype is restored

Front 18

What’s the two types of revertant mutations

Back 18

Same site and second site

Front 19

What is same site revertant

Back 19

Mutation is at the same site as original mutation

Front 20

What what is a second site revertant

Back 20

Mutation is at a different site in the DNA

Front 21

What is a suppressor mutation

Back 21

Mutation that compensated for the effect of the original mutation

Front 22

What is the error rate in DNA replication

Back 22

10-6 to 10-7 per kilo base

Front 23

What are the mutation rates in RNA genomes compared to DNA

Back 23

1000 fold higher

Front 24

What are the different types of mutagens

Back 24

Chemical

Physical

Biological

Front 25

What are the classes for chemical mutagens

Back 25

Nucleotide bass analogs- resemble nucleotides

Inducers if chemical modifications

Chemical mutagens that cause frameshifts

Front 26

What are the two main categories of mutagenic electromagnetic radiation

Back 26

Nonionising

Ionising

Front 27

What are examples of nonionising mutagens

Back 27

Uv radiation

Front 28

What is an example of ionising mutants

Back 28

X rays

Gamma rays

Cosmic rays

Front 29

What absorb nonionsing mutants

Back 29

Purines and pyramidines

Front 30

What are the three types of DNA repair

Back 30

Direct reversals

Repair of single strand damage

Repair of double strand damage

Front 31

What is direct reversal DNA repair

Back 31

Mutated base still recognisable and can be repaired without referring other strand

Front 32

What are ss damage repairs in DNA repair

Back 32

Damaged DNA is removed and repaired using opposite strand as template

Front 33

What if ds DNA repair

Back 33

SOS regulatory system

Allows relocation to proceed and cell to replicate but errors more likely

Translesion synthesis allows DNA to be synthesised with no template

Front 34

What is translesion

Back 34

Synthesis allows DNA to be synthesised with no template

Front 35

What is recombination

Back 35

Physical exchange of DNA between genetic elements

Front 36

What is homologous recombination

Back 36

Process that results in genetic E change between homologous dna from two different sources

Selective medium can be used to defect rare genetic recombinants

Front 37

What are transposable elements

Back 37

Discrete segments if DNA that move as a unit from one location to another within tiger DNA molecules

Front 38

Where can transposable elements be found

Back 38

Three domains of life

Front 39

What are the two main types of transposable elements

Back 39

Transposons

Insertion sequences

Front 40

What is an insertion sequence

Back 40

Around 100 nucleotides long

Inverted repeats 10-50 bp

Only gene is for the transposase

Found in plasmid and chromosome of bacteria and archaea

In some bacteriophages

Front 41

What is a transposon

Back 41

Moves any DNA between inverted repeats

Insertion of transposable element generates a duplicate target sequence

May include antibiotic resistance (Tn5 and Tn10)

Front 42

What are the two types of transposition

Back 42

Conservative and replicative

Front 43

What is conservative transposition

Back 43

Transposon is excused from one location and reinserted at a second location number of transposons stays consistent

Front 44

What is replicative transposition

Back 44

A new copy of transposon is produced and inserted at a second location number of transposons present doubles

Front 45

How do you make mutants with transposons

Back 45

transposons with antibiotic resistance used

transposons is on a plasmid that can’t be replicated in cell- temperature sensitive replicon

Cells capable of growing on a lecture medium likely acquired transposons

Screened for miss of function to determine insertion site

Mutated gene tagged with resistance marker

Front 46

What does CRISPR stand for

Back 46

Clustered regulatory interspaced short palindromic repeated