Lecture 6: Mutation and Repair Flashcards
(81 cards)
______: Due to a lesion (i.e. error) in DNA that is not repaired prior to replication round
mutation
Heritable change in nucleotide sequence which can affect change if mutation impacts a
______ (i.e. gene, promoter, binding site, etc.)
function
Note that Bacteria is _____ (i.e. one gene copy) so mutation can be observable
haploid
_________:
* Occur during normal growth due to biological errors
* e.g. replication errors 10-6 to 10-7/1000 bp (average gene size)
Spontaneous mutations
_______
* Caused by external factors (e.g. UV, chemicals, molecular techniques)
* Can increase mutation rate to ~ 10-3/1000 bp
Induced mutations
Change(s) due to mutation(s) can be:
___, _____, or _____
- Beneficial, detrimental or neutral (i.e. no effect)
Strain of an organism isolated from nature → _____
wildtype
A cell derived from the wild type whose genome carries a change in nucleotide
sequence from that of the wildtype genotype → _____
mutant
Observable properties of a strain → phenotype
* If changed from wildtype, than is referred to as a _____ phenotype
mutant
T/F: Mutant derivatives can be obtained from either directly from a wild-type strain or from
another strain (i.e. parental) previously derived from the wild-type.
true!! Note: depending
on the mutation, a mutant may or may not differ in phenotype from its parent
E. coli wild-type and mutant strains grown on MacConkey agar (selective and
differential medium) containing maltose as carbon source, and pH indicator that
turns ____ (i.e. acidic) if maltose is fermented
red
______ metabolism: Metabolic pathway encoded by 4 monocistronic and 4 polycistronic
transcriptional units for a total of 8
maltose
T/F: Virtually any characteristic of an organism can be changed
by mutation
true
_______:
* Confers a clear advantage on the mutant strain under
certain environmental conditions, such that the progeny of
the mutant cell are able to grow and replace the parent
Selectable mutations
Example: antibiotic-resistant mutant that can grow in the
presence of an antibiotic that inhibits or kills the parent
and is thus selected under these conditions
_______:
* Confers neither an advantage or disadvantage over their
parent cells when grown in laboratory conditions
* Can detect by “screening” morphologies of colonies for
differences
Non-selectable mutations
______
* Selection is preferred over screening because selective conditions typically place
such severe restraints on the population that mutants are easily detectable
Genetic experiments
_______:
* A mutant strain with an additional nutritional requirement above that of the wild-type or
parental strain (i.e. prototroph) from which it was derived
Nutritional Auxotrophs
______ – are those that occur without external intervention, and most result from
occasional errors in the pairing of bases by DNA polymerase during replication
Spontaneous mutation
______ – are those caused by environmental agents such as UV light that alters the
structure of bases in the DNA, and chemicals that chemically modify DNA → mutagens
Induced mutation
_______ (a.k.a. base-pair substitutions)
* Mutations that change only one base pair
* Change, if any, in phenotype depends on where in the genome the mutation occurs and
the nature of the mutation
Point mutations
transitions or transversions, silent mutations, missense mutation, nonsense mutation
_____ mutation – change within a base category (A to/from G; C to/from T)
Transition
______ mutation – change between base categories (A/G to/from C/T)
Transversion
If a point mutation is within the region of a gene that encodes a polypeptide, any change in the phenotype of the cell is most likely the result of a change in the ________ of that polypeptide
amino acid sequence
______ in coding
regions are almost always in the
third base of the codon because
of genetic code degeneracy
Silent mutations
