DNA mutations Flashcards
what do mutations start with
a replication error that isn’t caught
mutations fall in one of three categories
beneficial mutations
neutral mutations
deleterious mutations
most mutations are
neutral or slightly deleterious
changes one amino acid
missense mutation
creates a change in a base that does not change an amino acid
silent mutation
changes an amino acid to a stop codon
nonsense mutation
when a base is either added to or removed from an mRNA sequence, it will cause a shift in the sequence of frame
insertion or deletion
an increase in the number of each type of chromosome
polyploidy
the addition or deletion of a chromosome
aneuploidy
occur when sections of a chromosome break and rotate before rejoining the chromosome
inversions
occurs when a broken section of one chromosome becomes attached o another chromosome
translocation
chromosome level mutation can be visualized via
karyotypes
strand of DNA is the same as the mRNA sequence
sense strand
strand in DNA that is copied by RNA polymerase into RNA
antisense strand
all amino acids except two are encoded by more than one codon
redundant
one codon never codes for more than one amino acid
unambiguous
a few minor exceptions, all codons specify the same amino acids in all organisms
nearly universal
the first two bases are usually identical when multiple codons specify the same amino acid
conservative
how many bases specify a single amino acid
three
what is the start codon
AUG
what are the stop codons
UAA
UAG
UGA
mechanisms for point mutations typically act through three primary processes
base replacement
base alteration
base damage
example of base replacement
analogues
example of base alterations
chemical modifications
example of base damage
disrupt base-pairing
the spontaneous isomerization of a nitrogenous base to/from keto and enol forms or to/from amino and imino forms
tautomeric shift
what type of mutations to tautomeric shifts cause
transition mutations
where one purine/pyrimidine base pair is replaced with the other purine/pyrimidine base pair
transition mutations
removal of amino groups from nitrogenous base
deaminations
if cytosine is deaminated what is created
uracil
if 5-methylcytosine is deaminated what is created
thymine
add ethyl groups to normal base
alkylating groups
adds hydroxyl groups to normal base
hydroxylating agents
hydrolysis of glycosidic bonds
depurination
purine bases are hydrolyzed where
at the ribose glycosidic linkage, leaving the sugar-phosphate backbone in tact
most commonly incorporated, leading to a transition mutation
adenine
