bio10 - shawn3387

[ArchivalUser]

Which is the most correct sequence of events in gene repair mechanisms
in patients without a mutated repair process?
a. Nicking, excision, replacement, sealing, recognition
b. Sealing, recognition, nicking, excision, replacement
c. Recognition, nicking, excision, replacement, sealing
d. Nicking, sealing, recognition, excision, replacement
e. Nicking, recognition, excision, sealing, replacement

[ArchivalUser]

C...

[ArchivalUser]

ccc

[ArchivalUser]

CC

[ArchivalUser]

c.

[ArchivalUser]

The answer is c. (Murray, pp 412“434. Scriver, pp 3“45. Sack, pp
3“29. Wilson, pp 99“121.) In all of the forms of DNA repair in normal cells,
a common sequence of events occurs.
1. The single or multiple base abnormality is surveyed and detected by a
specific protein or proteins.
2. The DNA is nicked on one side of the damaged DNA.
3. A specific enzyme excises the damaged portion (steps 2 and 3 can be
combined if an excinuclease cuts on both sides of the damaged DNA).
4. The damaged portion of the strand is replaced by resynthesis catalyzed
by DNA polymerase I.
5. A ligase seals the final gap.
With some variability, these general principles apply in nucleotide excision
repair (segments of about 30 nucleotides), base excision repair of single
bases, and mismatch repair of copying errors (one to five bases).