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BIO SCI 99 Study Guide - Midterm Guide: Point Mutation, Tautomer, Purine

Biological Sciences
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Lecture 10 DNA Repair Part I
I. Mutations
What is the difference between errors/damage and mutations? When does
error/damage become a permanent mutation?
1. Point mutations
What is a point mutation? How are they caused? Why do some point mutations in
a protein-coding gene result in an amino acid change while other point mutations
do not cause an amino acid change? Why do still other point mutations cause
truncated proteins? What are the specific terms used to refer to each of these
three outcomes?
2. Small insertions and deletions (indels)
What are indels? How are they caused? What happens when the number of
nucleotides inserted or deleted in a protein-coding gene is not a multiple of
three? What is the usual outcome for the encoded protein in this case? What is
the significance of ‘multiples of three’? (You might have already answered this
question when thinking about the different possible effects of point mutations.)
What effect can a short sequence repeated many times in a row have on the
replication of that sequence? What genetic disease example given in lecture is
caused by this effect through having many three nucleotide repeats in a row in a
protein coding gene? How many repeats does an individual have to have to be
considered a carrier? What is the general name for this phenomenon? Do carriers
of the mutation always have symptoms?
3. Large chromosomal rearrangements
How are chromosomal rearrangements caused? Give some examples of types of
chromosomal rearrangements. What deleterious effects can these
rearrangements have? Are they often inherited? How does the BCR-ABL fusion
gene result in cancer?
II. Sources of DNA alterations
1. Polymerase errors
Errors can result from mispairing and slippage along the template or daughter
strand. What is a tautomer?
What do the terms transition’ and transversion’ mutation mean? Is a
polymerase as likely to mistake one purine for another as it is to mistake one
purine for a pyrimidine (or vice versa)?
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