cycle 4

Question 1

mechanism of proofreading

Answer 1

corrects errors made by DNA polymerase during replication
facilitated by DNA polymerase. as enzyme adds complementary nucleotides, simultaneously checks for errors in base pairing. if error found, DNA polymerase utilizes exonuclease activity to remove the mismatched nucleotide from the 3’ end

Question 2

mechanism of mismatch repairs

Answer 2

corrects errors made during replication that escape proofreading
mismatch repair system scans newly formed DNA for any inaccuracies in the base pairing. if error detected, mismatch repair proteins excise incorrect nucleotide, and correct nucleotide is inserted

Question 3

mechanism of excision repair

Answer 3

corrects various kinds of DNA damage, such as those cause by chemicals and radiation
specialized proteins recognize region of damaged DNA. damaged segment is excised or cut out by endonucleases. DNA polymerase synthesizes new strand. ligase seals gaps

Question 4

when each mechanism is most likely to be used

Answer 4

proofreading - during DNA replication
mismatch repair - after DNA replication. is important in the prevention of cancer
excision repair - after exposure to environmental factors causing DNA damage (UV radiation, chemicals)

Question 5

difference between DNA damage and mutation

Answer 5

mutation - double-stranded change in the base sequence of a region of DNA
damage - changes that affect only one strand of the double helix

Question 6

types of DNA damage

Answer 6

exogenous, endogenous

Question 7

exogenous damage

Answer 7

outside, from environment, damage DNA directly
UV light, chemicals (smoking, medication, air pollution)
ionizing radiation

Question 8

endogenous damage

Answer 8

inside cell
metabolism (in mitochondria, electron transport chain - only place where electrons flow singularly. electrons bind with O2, ROS (reactive oxygen species) damages DNA)