module 10 Flashcards
mutation
heritable change in the genetic material
homologous recombination
the exchange of identical or similar DNA segments between homologous chromosomes
point mutation
a change in a single base pair
base substitution transition
a change of a C/T–>T/C or A/G–>G/A
base substitution transversion
a change of a C/T–>A/G or A/G–>C/T
silent mutations
base substitutions that do not alter the amino acid sequence of the polypeptide
missense mutation
base substitutions in which an amino acid change does occur
nonsense mutation
base substitutions in which causes an early stop codon occurs
frameshift mutation
an addition or subtraction of nucleotides that isn’t in a group of three
forward mutation
changes the wild-type genotype into some new variation
reverse mutation
changes a mutant allele back to the wild-type
suppressor mutation
reverse the phenotypic effects of another mutation
chromosomal breakpoint
site of breaking and rejoining
position effect
when a gene is left intact but its expression may be altered because of its new location
germ-line mutations
those that occur directly in a sperm or egg cell
somatic mutations
those that occur directly in a body cell that is not apart of the germ-line
spontaneous mutations
result from abnormalities in cellular/biological processes
induced mutations
caused by environmental agents
depurination
the removal of a G or A from the dna (apurinic site)
deamination
removal of an amino group from the cytosine base
tautomeric shift
a temporary change in base structure
reactive oxygen species
Hydrogen peroxide, superoxide, hydroxyl radical
oxidative stress
an imbalance between the production of ROS and an organism’s ability to break them down
oxidative DNA damage
ROS over-accumulation causes a transversion mutation
trinucleotide repeat expansion
when the length of a trinucleotide repeat has increased above a certain critical size
mutagens
agents that alter the structure of DNA and thereby cause mutations
base modifiers
covalently modify base structure, disrupt pairing by alkylating bases
intercalating agents
directly interfere with replication process
base analogues
incorporate into DNA and disrupt structure, tautomerize at a high rate
mutation rate
the likelihood that a gene will be altered by a new mutation
mutation frequency
the number of mutant genes divided by the total number of genes in a population
ames test
evaluates mutagenicity
Nucleotide excision repair (NER)
can repair thymine dimers, missing bases, and some types of crosslinks
NER mechanism
- uvra,b,c,d recognize and remove a short segment of damaged DNA
- DNA polymerase and ligase finish the repair job
translesion synthesis
specialized enzymes assist DNA pol to go over aberrant structures in the templet strand
gene conversion
when one of the alleles is converted to the other
