Lecture 02: Mutations Flashcards
what is mutation?
changes in the sequence of the DNA
in eukaryotes, mutations can occur in: ________ and _________
somatic and germline cells
types of mutation
- according to size
- effect on gene function
- effect on DNA
- effect on protein
- direction
what are the types of mutation according to size?
- point
- segmental
types of mutation that has an effect on gene function
- loss of function
- gain of function
type of mutation that has an effect on DNA
- structural
- spatial
what is structural mutation?
change in nucleotide content
different DNA structural mutation
- substitution
- deletion
- insertion
types of substitution mutation
- transition
- transversion
which type of substitution mutation is more usual in nature?
transition
types of DNA spatial mutation
- inversion
- translocation
it is the inability to clot blood
Hemophilia
in what clotting factor are Hemophilia A and B deficient in?
VIII and IX respectively
types of mutations that have an effect on protein
- silent
- nonsense
- missense
- neutral
- frameshift
what is nonsense protein mutation?
normal codon to a stop codon
what is missense protein mutation?
change in amino acid that changes protein function
sickle cell anemia is what type of mutation?
missense mutation; Glu to Val
types of mutations based on direction
- forward
- reverse
what are the origins of mutation?
- spontaneous
- error-prone replication bypass
- errors in DNA repair
- induced
what is spontaneous origin of mutation?
mutation due to molecular decay
types of spontaneous origin of mutation
- tautomerism
- depurination
- deamination
- slipped strand mispairing
what is tautomerism?
base change due to repositioning of H
what is depurination?
hydrolysis of a purine (A or G)
what is deamination?
removal of amine group in C or A, resulting in U or hypoxanthine, respectively
what is slipped strand mispairing?
denaturation of the new strand from replication then renaturation in a different spot
what is error-prone replication bypass?
an origin of mutation that allows the DNA replication machinery to replicate past DNA lesions
what is mutation caused by errors in DNA repair?
repair in double strands breaks in DNA that sometimes lead to errors
pathway involved in mutation caused by errors in DNA repair
non-homologous end joining pathway
what is induced origin of mutation?
mutation caused by mutagenic agent or environment
types of induced origin of mutation
- non-ionizing radiation
- ionizing radiation
- chemicals
example of non-ionizing radiation?
UV light
describe ionizing radiation as origin of mutation
results in deletions or insertions in DNA
examples of chemicals that cause mutations
- base analogs
- intercalating agents
- alkylating agents
- oxygen radicals
different repair mechanisms for mutations
- photoreactivation
- excision repair
- mismatch repair
- SOS repair
what is photoreactivation repair mechanism?
removal of damaged DNA by light-dependent enzyme
gene that encodes the enzyme that removes the damaged DNA via photoreactivation
phr gene
what is excision repair?
excision of damaged part
enzyme involved in excision repair
DNA pol I
what is SOS repair?
allows DNA replication to bypass lesions or errors in the DNA
these are the regions in the genome that are more prone to mutations than others
hotspots
what is pseudogene?
resembles functional genes but contain defects that prevent it from being expressed
