Nature of Mutations

Question 1

What is a model system?

Answer 1

An organism/type of organism with that can be exploited to understand all forms of life.

Question 2

Advantages of microbial models for genetics

Answer 2

• Rapid reproduction time (E.coli 2x in 20mins)
• Cheap to maintain
• Large populations - spontaneous mutants occur
• Selection of mutants is easy

Question 3

Advantages of bacteria as a model

Answer 3

• Haploid - phenotype seen immediately + simple genetic analysis
• Small genomes
• Genetic knockout/manipulation is simple
• Can easily create strains with desired mutations

Question 4

Advantages of microbial genetics models for microbiology

Answer 4

• Ecology
• Cell Biology
• Pathogenicity
• Evolution
• Biotech

Question 5

Steps for forward/classical genetics

Answer 5

1) Random genome mutagenesis
2) Phenotypic Screening
3) Genetics Analysis (Mapping)
4) Gene isolation
5) Gene seq determination (protein study)

Question 6

Advantages/Disadvantages of f/c genetics

Answer 6

A) Emphasis on phenotype and the genes responsible.
A) Can find conditional lethal mutants
D) Slow
D) May not be possible to find all the genes for a given phenotype

Question 7

Historically, how did reverse genetics work?

Answer 7

Start with a protein product, find a gene in the library via:

• protein N-terminal seq (DNA which hybridises to a degenerate oligonucleotide probe)
• antibody protein detection

Question 8

How does reverse genetics work today?

Answer 8

• Focus on gene of interest (may have homology in another microbe)
  1) Mutate gene in vitro
  2) Substitute gene for the wild type allele
  3) Determine mutant phenotype

Question 9

What are some types of mutant uses?

Answer 9

• Matching a protein to a function
• Determining lethal mutations -> essential genes
• Cloning genes with gene libraries

Question 10

What are the two yeasts that Paul Nurse used in his cell cycle complementation experiment?

Answer 10

Schizosaccharomyces pobme

Saccharomyces cerevisiae

Question 11

What human gene did he clone and what method did he use?

Answer 11

cdc2

Complementation with a yeast mutant

Question 12

What is Base Tautomerism?

Answer 12

A base with a reposition hydrogen atom that alters the hydrogen bonding pattern

Question 13

What do tautomers lead to?

Answer 13

Incorrect base pairing

Question 14

What tautomer form leads to an AC pairing?

Answer 14

imino

Question 15

What tautomer form leads to TG pairing?

Answer 15

enol

Question 16

What point mutation forms as a consequence of innate chemical properties?

Answer 16

Spontaneous Deamination mutations

Question 17

What SD mutations are easily detected?

Answer 17

C -> U, A -> HX

U, and HX are atypical DNA bases. They are recognised easily.

Question 18

What SD mutation is not easily detected?

Answer 18

5MeC -> T

Question 19

What is slipped strand mispairing?

Answer 19

Denaturation followed by renaturation in a different spot, during replication

Question 20

Pathogenic bacteria switch gene expression of what proteins on and off by SSM?

Answer 20

Surface exposed proteins - immune evasion called Phase Variation.

Question 21

What systems remove DNA lesions?

Answer 21

Proof-reading by DNA pol.

Mismatch repair enzymes.