DNA damage and repair Flashcards
-understand mechanisms through which mutations arise -understand the major DNA repair systems -know examples of diseases caused by DNA repair deficiency -understand why there is RNA -learn how transcription is similar to replication but different
Name 3 alkylating agents
- nitrogen mustard
- ethylnitrosourea
- MNNG
What’s a common alkylation product?
O6-methylguanine
O6-methylguanine is formed when a ______ group is added onto the _____ molecule of guanine, and now it can base pair with either cytosine or ______
methyl
oxygen
thymine
What can remove the methyl group off of O6-methylguanine?
MGMT
True of False: MGMT is a protein, but not an enzyme. This is because it can only be used once and is not degraded thereafter.
True
MGMT transfers the methyl group from O6-methylguanine onto a ______ residue in its active site.
Cysteine
True or False: Sunshine causes pyrimidine dimers (which are usually thymine, but can be cytosine)
True
When UV light comes in, it can cause an electron from the double bond between thymine to go between adjacent thymines, where now there is a ______ distance b/t the thymines and a _____ is created in the helix
shorter
distortion
Thus UV can lead to _____ thymine dimers or a ___ photoproduct
cyclobutane
6-4
Which product of UV radiation is most dangerous?
the 6-4 photoproduct
True or False: Humans also have DNA photolyase.
False: DNA photolyase is present in bacteria.
What is MTHF?
a photon antenna that absorbs UV-A and becomes photoexcited
What happens after MTHF absorbs UV-A and becomes photoexcited?
It transfers photoexcitation to FADH
FADH transfers an electron to the dimer, breaking it into monomers, then ……….
takes the electron back (reforming the double bond)
True or False: DNA photolyase does a base-flipping mechanism to expose the dimers that need to be fixed
True
