chapter 35 Flashcards
DNA damage includes
incorporation of an incorrect base, insertions, deletions, or breaks in one or both strands
DNA damage may lead to
cell death or uncontrolled
replication, as when normal cells are transformed into cancer cells
chemicals that alter specific bases after replication is complete are called
mutagens
what is oxidation of DNA bases
hydroxyl radicals oxidize guanine to 8-oxoguanine, which base-pairs with adenine instead of cytosine during the next round of replication
deamination causes what
adenine to be deaminated to form hypoxanthine, which pairs with cytosine instead of thymine
what does ultraviolet radiation do
covalently links adjacent pyrimidines, blocking replication
what is an example that may cause breaks in DNA strands
X-rays
what is alkylation damage
when bases interact with hydrocarbons
what does alkylation do
GC to AT
what is the basic DNA repair system mechanisms
- recognize inappropriate base(s)
- remove inappropriate base(s)
- fill in the resulting gap with DNA polymerase I and DNA ligase
how does the first DNA repair step occur
DNA polymerase proofreads the newly synthesized DNA and corrects mismatches
mismatch repair systems correct errors are NOT corrected by proofreading
true
direct repair corrects mistakes….
without having to remove any fragments of DNA
what does DNA photolyase do
uses light energy to cleave pyrimidine dimers
what are the 3 types of DNA repair
proofreading
mismatch repair
direct repair
