10.3 Flashcards
(23 cards)
what are the two types of mutations (in terms of transmission?
somatic mutations - not transmitted
germ-line mutations - may be transmitted to ~50% of offspring
what are the classifications of point mutations based on aa’s?
silent/synonymous - no change
missense/nonsynonymous - 1 aa changes
nonsense - stop codon
what are the classifications of point mutations based on affect on sequence?
indels cause frameshifts that alter reading frames (missense or nonsense) - except when they occur in groups of 3
indels outside of reading frames have no effect
what are the classifications of mutations based on functional phenotype?
loss-of-function - recessive inheritence
gene-of-function (new/wrong gene product) - dominant inheritence
neutral
what are transitions vs transversions?
transitions - purine/pyrimimide swap
transversions - purine/pyrimimide stay the same
do transition or transversion mutations happen more often?
transitions
what are forward vs reverse mutations?
forward alters wild phenotype
reverse changes mutant back to wild phenotype
what are suppressor mutations?
mutation that suppresses a previous mutation
what are the two types of suppressor mutations?
intragenic (same gene)
intergenic (diff gene)
how do mutations happen?
spontaneously or induced
what are the three types of spontaneous mutations?
tautomeric shifts (of bases) during DNA rep
DNA strand-slippage during DNA rep
misalingment of homo chromosomes during crossing over (recomp) at meiosis I
what are tautomeric shifts?
small chemical changes in bases that change which base they can bind to
what is DNA slippage?
strands slip into small loops which results in adding/leaving out a nucleotide
what are mutagens?
agents that cause mutations:
radiation or chemical mutagens
what is ionizing radiation?
dislodges electrons to cause free radicals/ions that alter base structure and break phosphodiester bonds
what is ultraviolet radiation?
weaker ionizing radiation
comes from sun
causes pyrimidine dimers that blocks DNA rep
how do we repair damaged DNA from UV?
protein recognizes mismatches and unwinds, excises nucleotides, fills in correct nucleotides
what is xeroderma pigmentosum?
autosomal recessive genetic disorder where cells cannot repair mutations caused by UV light
what are base analogs?
chemical mutagen that look like bases but cause incorrect pairing and point mutations
what are base-modifying agents?
chemical mutagens that change bases to pair incorrectly and cause point mutations
what are intercalating agents?
chemical mutagen that distort normal base stacking and cause insertion/deletion of a base pair
what is the ames test?
method to mutagens by comparing growth reversions of salmonella on different mediums (mutagens will cause growth)
what does rat liver enzyme do in the ames test?
mimic chemical modification of potential mutagens in human body (could make chemical more or less mutagenic)