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14 Cards in this Set
- Front
- Back
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spontaneous mutations |
changes that result from normal cell processes occur randomly at infrequent but characteristic rates base substitution most common; leads to 3 possible outcomes (silent, missense, nonsense) |
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point mutation |
change of a single base pair |
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silent mutation |
wild-type amino acid a single base pair substitution that codes for the same codon and does not alter the protein |
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missense mutation |
different amino acid a single base pair substitution that codes for a different codon resulting protein may only partially function (termed: leaky) |
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nonsense mutation |
a single base pair substitution that codes for a premature stop codon which yields a shorter protein (specifies stop codon yields shorter protein) |
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stop codons |
UAA (you are away) UGA (you gone away) UAG (you are gone) |
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frameshift mutations |
deletion or addition of nucleotides 3 pairs changes one codon; impact depends on location within protein alters reading frame, one amino acid more or less often results in premature stop codon shortened, nonfunctional protein; knockout mutation |
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null/knockout mutation |
a mutation that inactivates gene |
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induced mutations |
result from outside influence mutagen: agent that induces change 2 general types: chemical & radiation |
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chemical induced mutation |
Chemical mutagens: may cause base substitutions or frameshift mutations Some chemicals modify nucleobases by exchanging base-pairing properties Base analogs resemble nucleobases which can mistakenly be incorporated by DNA polymerase |
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intercalating agents |
Cause frameshift mutations Flat molecules that intercalate (insert) between adjacent base pairs in DNA strand Pushes nucleotides apart, produces space Causes errors during replication If in template strand: a base pair is added to synthesized strand If in strand being synthesized: a base pair is deleted, which often results in a premature stop codon |
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Radiation |
2 types: UV irradiation and X rays |
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UV irradiation |
Forms thymine dimers (covalent bonds between adjacent nucleotides which distorts DNA molecule) Replication and transcription stall at distortion Cells will die if damage not repaired Mutations results from cell's SOS repair mechanism Fixed by "photoreactivation" (only prokaryotes) and excision repair |
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X rays |
Cause single- and double-stranded breaks in DNA Double strand breaks often produce lethal deletions Can alter nucleobases |
