DNA damage response Flashcards
double helixes replicated from 1 chromosome are nwow called sister chromatids, once separated from its sister then its called
chromosome
mismatch repair - wrong base binds to each other causing a kink.
protein muts comes along and recognises and binds mismatch due to shape
mutL recognises the kink in new strand
DNA polymerase fills gap
DNA ligase binds the strands together
true
genes such as MSH2 and MLH1 are involved in making proteins for mismatch repair - what cancer can this lead to
HHNPCC
colon cancer
bases excision repair
cellular homeostasis is a delicate balance between the rate and magnitude of oxidant formation and the rate of oxidant elimination
overproduction leads to oxidative stress which can damage single bases or nucleotides. most common type called 8-oxyguanine resulting is mismatched pairing therefore instead of G-C get G-A
this is dealt with by base excision repair
DNA glycoylase recognises damaged base and cleaves between base and backbone
endonuclease cleaves phosphodisester backbone near AP site.
DNA polymerase intimates repair synthesis ( exonculeuas)
DNA ligase buts backboen together
true
different form is xeroderma pigmentossum XP which can lead to skin cancer, UV sensitivity and neurological abnormalities what process is affected
nucleotide excision repair
double strand break repair
mediated by ku proteins
DNA ligase joins to ends
however if the break Is not clean - DNA synthesis and insertion of a few new bases and then ligation
anther method is some are eating away ending up with a deletion
small amount of overlaps chopped away creating blunt ends joined together
all these methods and end pathways end up in mutation
ligase
Joins DNAstrands together
endonuclease
Cleaves the phosphodiester bond within DNA
exonuclease
Removes successive nucleotides from the end of a polynucleotide molecule.
sister chromatids
Identical copies formed by the DNA replication of a chromosome, joined by a common centromere.
Two types of UV light are proven to contribute to the risk for skin cancer: Ultraviolet A (UVA) has a longer wavelength, and is associated with skin aging. Ultraviolet B (UVB) has a shorter wavelength and is associated with skin burning.
which type of UV provides the energy your skin need to make vitamin D
UVB
which type of UV light cause people to tan
UVA
nucleotide excision repair
pyrimidine dimers cause distortion in DNA double helix these block replication and transcription
two excision endoncueluases bien DNA to site of lesion
one cleaves each side and removed by helciase
DNA polymerase fills the gap
DNA ligase seals the nick
true
XP - Xeroderma pigmentosum
autosomal recessive due to impaired nucleotide excision repair
3rd stage of developemetnt leads to skin cancer the three types
detected infancy around 1-2 years and presents with sunburn
treated with gene therapy and methods of prevention
Symptoms include a severe sunburn after only a few minutes in the sun
Half have skin cancer by age 10, life expectancy is ~30 years less than normal.
Mutations in any of at least seven genes, XP-A through XP-G, cause xeroderma pigmentosum.
Xeroderma pigmentosum (XP) is a very rare skin disorder where a person is highlysensitive to sunlight, has prematureskin ageingand is prone todevelopingskin cancers.Xeroderma pigmentosumis caused bycellularhypersensitivityto ultraviolet (UV) radiation, as a result of a defect in theDNArepair system
proteins involved in homology directed repair of double stranded breaks
Double-strand breaks causes ATM auto phosphorylation
Phosphorylates several key proteins leading tocell cyclearrest, DNA repair or apoptosis including P53 - regulates cell cycles BRCA1 BRCA2 Take home: Homology dependent repair
