Mutations Flashcards
mutations always change ________
genotype of organism
genotype
complement of genes organism possesses
phenotype
physical expression of genes
appearance, chemical and structural characteristics of individuals
effect of mutation on organism depends on
where it occurs and how much the protein changes
sickle cell anemia
1 DNA base change in gene for hemoglobin changes 1 amino acid
glutamate (GLU) is replaced by valine (VAL)
neutral mutations
do not affect survival
may occur in unexpressed regions of DNA
beneficial mutations
rare
antibiotics resistance in bacteria
2 forms of mutations
- spontaneous
2. induced
spontaneous mutations
occur naturally during replication or form as misalignment deletions
induced mutations
caused by mutagens
3 types of mutagens
- chemical
- physical
- biological
chemical mutagens
chemicals mimic DNA bases or alter normal bases
AZT- mimics thymine
acyclovir- mimics guanine
aminopurine- mimics adenine
bromouracil- mimics thymine; binds guanine not adenine
nitrous acid- alters adenine to bind cytosine not thymine
physical mutagens
uv light and ionizing radiation
uv light
non ionizing, non penetrating rays
cause thymine dimers in DNA of skin from sunburn
thymine dimers
adjacent thymines bind laterally
may cause melanoma
xeroderma pigmentosum
genetic disease
tumors in response to uv
ionizing radiation
penetrates barriers
damages DNA
biological mutagens
transposons
“jumping genes”
control own movement- move around genome
cause mutations when inserted into other genes
5 mutation patterns
- base substitution
- frameshift
- inversions
- duplications
- translocation
base substitution
point mutation 1 DNA base changed to another a. missense b. silent c. nonsense
missense mutation
changes codon at 1st or 2nd DNA base
alters codon meaning to change amino acid
alters amino acid sequence of protein- may change protein function
sickle cell anemia
silent mutation
changes 3rd base of codon
usually codes for same amino acid
usually no effect on protein function
nonsense mutation
base substitution forms stop codon
protein synthesis stops before correct termination point
frameshift
insertions and deletions
shift codon reading frame to change amino acid sequence
inversions
reverse DNA base sequence of gene
duplications
inserts additional copies of DNA sequence into genome
translocation
DNA moves from 1 chromosome to another
Down’s syndrome
