Housekeeping

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Housekeeping

• Exams back today
• Childrens book due Friday
• Lab
• Read paper (maybe more than once)

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How do mutations occur?

• Natural
• DNA replication
• Depurination, Deamination
• Meiosis-unequal crossing over
• Transposons
• Mutagens increases natural rate of mutation
• Chemical
• Physical

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Chemical
Xray
UV light
Fig. 6.6c
Fig. 6.6d
Oxidation
Fig. 6.6e
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How do mutagens work?
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Mutagens How do they alter the DNA?

• DNA fragmentation
• inversions, deletions, rearrangement
• Insertion of base analogs
• Base substitution
• molecules with similar chemical structure but
  pair with different nucleotides (5-Bromouracil)
• Intercalators
• disrupts DNA replication, repair, recombination
• ethidium bromide, acridine orange

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What are the advantages to mutations?
Disadvantages?
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Why study mutations??
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Why study mutations?

• Evolution
• Natural selection
• How species change
• Study gene function
• Identify new genes
• Knock out a gene, see what is missing
• Study gene interaction
• Identify biochemical pathways
• Better molecular understanding of the cell!!

9
Discussion questionA St. Olaf graduate who
continued to get her Ph.D. is studying the
antimicrobial resistance pathways in bacteria.
Through her research, she has found two different
mutants that are both resistant to ampicillin.
Describe how she might have created these
mutants.
Her next step. What genes are these mutations
in? What might be the first step in determining
where these mutations are located?
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Complementation testing

• 2 mutations ? mate ? wild type
• 2 genes complement each other
• Are they on the same gene?
• Complementation groups
• Group of mutations that DONT complement each
  other
• ON THE SAME GENE
• Analyze heterozygote
• Two different mutant alleles

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Complementation testing
Fig. 6.13b
KEY Mutant allele recessive to wild type
(functional gene)
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Fly complementation test

• Mutation 1 garnet eye color
• Mutation 2 ruby eye color
• Heterozygote for garnet and ruby eyes
• Genotype?
• Do they complement each other?

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How many genes involved in eye color (How many
complementation groups)??
Complementation table
Fig. 6.13c
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Verify with linkage mapping!!
Fig. 6.13c,d
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Discussion question When might complementation
testing give false results?
INTRAGENIC RECOMBINATION Homologous
recombination within a gene Complementation!!
OrDominant mutant alleleNo complementation!
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Exam

• Average 38.5
• Range 26.5-50