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| heritable change in the DNA sequence of an organism's genome |
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| strain of any cell or virus that differs from its parental strain in genotype |
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| observable properties of the mutant |
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that which was isolated from nature
can refer to an entire organism or a particular gene |
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powerful genetic tool to isolate mutants from a large population via screening
tests to see if mutagen leads to increased reversions |
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| useful for identifying cells with a nutritional requirement for growth |
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| cells that have a nutritional requirement for growth |
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| mutations due to agents in the environment, including mutations made deliberately by humans and from chemical or radiation exposure |
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| mutations that occur without external intervention, largely result from occasional errors during DNA replication |
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| change only a single base pair, caused by base-pair substitutions or by the loss or gain of a single base pair |
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| mutation that does not affect the amino acid or the phenotype of the cell, often in the wobble position |
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| mutation often in the 1st or 2nd base of a codon, that changes the amino acid and alters the protein |
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| changes a codon to a stop codon preventing the entire protein from being synthesized |
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| mutation where one purine is substituted for the other purine or pyrimidine is substituted for other pyrimidine |
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| mutation where a purine base is substituted for a pyrimidine base or vice versa |
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| deletions or insertions that result in a shift in the reading frame |
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| transposable elements usually 700-1400 bp in length |
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| reversion or back mutation |
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Definition
| point mutation being changed back to its original form |
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| strains in which the original phenotype is restored from a point mutation |
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| mutation that restores the phenotype in the same location as the original mutation (point-mutation) |
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mutation is at a different site in the DNA than original mutation
functions as a suppressor mutation and compensates for the effect of the original mutation |
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| chemical. physical, or biological agents that increase the mutation rate |
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| resemble purine and pyrimidine bases yet display faulty pairing |
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| powerful mutagens that induce mutations more often that base analogs |
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| include the acridines, inserted between 2 bases and push them apart, leading to single insertions or deletions |
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Definition
type of mutagenic electromagnetic radiation that includes UV
purine and pyrimidine bases strongly absorb radiation, producing direct damage to DNA such as pyrimidine dimers |
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Definition
type of mutagenic electromagnetic radiation that includes X-rays, cosmic rays, and gamma rays
produces free radicals that damage macromolecules in cells and can fragment DNA |
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| mutation caused by UV light with two T bases connected |
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bases that although altered can still be identified and can be repaired without referring to the other strand
DNA repair process |
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| repair of single strand damage |
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Definition
DNA repair process
damaged DNA is removed and repaired using the opposite strand as the template |
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| repair of double strand damage |
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Definition
a break in the DNA repaired by recombinatorial mechanisms and often needs more error-prone repair mechanisms
DNA repair process |
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| part of SOS system that allows replication to proceed (survival) but organism has many mutations |
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| stall DNA replication which can be fatal |
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| stalled replication or other major DNA damage |
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| what activates the SOS repair system? |
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| lesions remain but are bypassed by special DNA polymerases that perform translesion synthesis |
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| regulon that is regulated by two proteins, LexA and RecA |
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Definition
| a repressor that normally prevents SOS regulon expression |
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| activated by presence of DNA damage, stimulates LexA to inactivate itself by self-cleavage, allowing expression of SOS regulon |
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| organisms that benefit from increased mutation rates in rapidly evolving environments |
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| permits screening of chemicals to determine which may serve as mutagens |
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