1. Which of the following enzymes is directly involved in base excision repair mechanism of mutations?
Glycosylases
Cyclic Adenosine Monophosphate
Serines Kinases
Helicases
Alkytransferases
2. Shown below is a list of types of repair systems or repair molecules (a-g) and types of DNA damage or mutations (1-6). On the blank line following each type of damage, write the letter(s) of all repair systems that can repair (or play a role in the repair of) that particular type of damage.
a) Photolyase
b) Base-excision repair
c) SOS repair
d) Alkyltransferases
e) Mismatch repair
f) Homologous recombination
g) Nucleotide-excision repair
1) Alkylation of G residues __________
2) Trinucleotide repeat expansion__________
3) Depurination __________
4) Pyrimidine dimers __________
5) Deamination __________
6) Double-stranded breaks __________

3. Determine which of the following repair pathways do not involve the use of a homology-dependent repair system?
Base excision repair
Photo reactivation repair
Transcription coupled repair
Nucleotide excision repair
Mismatch repair
4. What repair system exists in cells to repair damage of a single base via homology dependent repair? Describe the mechanism of this repair system.
5. Put the following events in order as they occur in recombination according to the "double-stranded-break model."
a. Cleavage of Holliday structures
b. Formation of loop in uncut duplex
c. DNA repair synthesis of second strand
d. Strand invasion
e. Double-strand break of one chromatid
f. Formation of Holliday structures
g. DNA repair synthesis of one strand