Repair of DNA

Question 1

there is the possibility of introducing mutations through errors in base-pairing. To limit this possibility, mismatched bases can be detected and repaired during replication.

Answer 1

Replicating DNA

Question 2

big cellular investment. there are a considerable number of genes that encode repair enzymes. each cell has multiple repair pathways and many checkpoints. most cells use the undamaged strand of the DNA as a template for repair, but they all have their own enzymes and preferences for recognizing damage.

Answer 2

DNA repair

Question 3

can mutations be good?

Answer 3

without them, we would not exist. some mutations confer selective advantages (sickle cell gives advantage over malaria). we need controlled variations/mutations to evolve, but we do not want damaging diseases to arise (many come from defective DNA repair mechanisms)

Question 4

Studying _______ revealed the mechanism of replication

Answer 4

bacteria (prokaryote)

Question 5

Errors that escape correction during replication can still be identified and repaired later by a

Answer 5

Mismatch mechanism

Question 6

Once ( ) are found, the incorrect match is excised (via exonuclease), replaced (via polymerase) with the correct nucleotide, and joined (via ligase) to its adjacent nucleotides in the strand.

Answer 6

Mismatches

Question 7

removes the wrong nucleotide adding by polymerase

Answer 7

nuclease

Question 8

acts as a built-in self-correction mechanism (proofreading); acts 3’ to 5’

Answer 8

Exonucleus activity

Question 9

exonucleus activity; DNA repair mechanisms; limits the accumulation of mutations

Answer 9

Self-correction mechanisms

Question 10

approximate number of nucleotides in the human genome

Answer 10

6 billion