Study guide
Chapter 8 (8-8.5), Lecture 4.25.12
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How do bacteria evolve over time?
What is horizontal gene transfer?
What is spontaneous mutation? Is it common or rare?
There are three different types of mutation—advantageous, neutral and disadvantageous. Make
sure you understand these concepts and an example of each one (note: the lecture includes an
example as the –‘ed point underneath the bullet points). If I give you a specific situation and ask
you what kind of mutation is generated, you should know enough about these terms to pick the
correct term
Is antibiotic resistance advantageous or disadvantageous? How does environmental setting play
a role in this?
What are three types of spontaneous mutation that we talked about?
o Base substitution
o Deletion or insertion
o Transposons
What happens to the DNA during each of these types of mutation (i.e. is it frame-shifted, does
the codon change, are large pieces of DNA moved)? Can you explain the process by which the
mutation may have occurred (for example, if I tell you a mutant has a frame-shift mutation, can
you explain to me what that means [that the codons are shifted such that an entirely different
set of codons are translated] and what kind of mutation might cause that kind of mutation).
What are transposable elements? How are they involved with antibiotic resistance?
The Sleeping Beauty transposon system is engineered by humans to insert a specific piece of
DNA into the chromosome. How can this be used in medicine?
What are induced mutations? How are these different from spontaneous mutations?
If guanine is methylated, creating methylguanine, what can it now base pair with instead of
cytosine? This is induced base substitution (it differs from spontaneous base substitution
because we are adding a chemical to create the methylguanine, which then pairs with the
wrong base pair, instead of the base substation happening randomly).
Base analogs can be introduced into the cells, which bind to the wrong base pair. How is this
similar in resulting mutation to the presence of methylguanine? Is this another form of base
substitution?
What kind of mutation do intercalating agents cause?
UV light can cause catastrophic damage to DNA by causing covalent bonds to be made between
adjacent thymines. What happens to transcription and DNA replication when they encounter
these dimers? At what point in this process does mutation occur in the DNA?
What are the different types of DNA repair?
Why does methylation of “old” (template) strand DNA matter in mismatch repair?
What method can a cell use to reverse UV damage in DNA in the light? In the dark?
What happens when there is a lot of UV damage?
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Why does the SOS response error-prone when fixing the damaged DNA?
What happens during the SOS response that allows the SOS genes to be transcribed (i.e. what is
the role of RecA and LexA in regulation)?
What is direct selection of mutants? Can you think of an example where we might use direct
selection?
What is indirect selection? When might we use this type of selection?
How does penicillin enrichment work? Why might it help us enrich for bacteria that are NOT
growing?
How can we use bacteria to test for mutagens? Why might we do this to test for potential
carcinogens?
What are the three types of horizontal gene transfer? What does DNA need in order to be
passed from mother to daughter cells?
What is conjugation?
How are plasmids transferred? What kind of genes can be passed via plasmids?
How can new DNA be incorporated onto a plasmid (chromosomal transfer and transposons)?
Plasmids are replicons, what does this mean?
Can bacteria conjugate to plant cells? What other method can inject DNA into plant cells?
What is transduction? Do you understand the steps of transduction? How does bacterial DNA
end up in a new bacterial cell via this method?
In transformation, what kind of DNA is taken up by the cells? How is this different from
transduction and conjugation? What happens to the daughter cells of a cell that has integrated
this DNA into its chromosomes (are they mutants or wild type?)
What must happen to transduced or transformed DNA in order for it to be propagated to
daughter cells? For plasmids to be propagated?