Cycle 4 (Workshop + Study Session) Flashcards
Define and state the types of DNA damage
Exogenous: Coming from outside the cell (e.x. UV, IR, chemicals)
Endogenous: Coming from inside the cell (e.x. Cell Metabolism (ROS), replication errors)
What is the difference between mutations and DNA Damage?
Mutations are changes in the double stranded DNA sequence, while DNA damage is any change to DNA that is not double stranded
True or False:
Genetic variation refers to DNA damage
False, genetic variation refers to mutations
Can DNA damage lead to mutations?
Yes
What are ROS?
Reactive Oxygen Species
Very electronegative and unstable, will take electrons away from any sort of molecule nearby to regain stability (Targets DNA)
What can taking electrons away from DNA lead to?
Double-stranded breaks
What is the Oxygen Paradox?
While oxygen is crucial to many cell functions, too much of it can ultimately lead to cell death
Too much oxygen causes _________ ______
Oxidative Stress
What helps our cells combat the effects of ROS?
Antioxidants
True or False:
DNA Polymerase can proofread during replication
True
How does DNA polymerase recognize that a mistake has been made?
Detection of distortion in the DNA backbone
How does DNA polymerase remove incorrect bases?
Moves backwards and removes the incorrect base through 3’-5’ exonuclease
True or False:
3’-5’ exonuclease can remove several bases at a time from the end of the chain
False, 3’-5’ exonuclease can remove bases one at a time from the end of the chain
Describe the _ steps in mismatch excision repair
4
Repair enzymes detect the distortion
Mismatch/repair enzymes bind to the damaged region and excise (cleave) the backbone through endonuclease activity
DNA polymerase fills in the gap
Ligase seals the nick
Define:
Mismatch repair
When the mistake is brought upon by mistakes by DNA polymerase III that are not fixed by proofreading
Define:
Excision repair
Used when there are exogenous sources of DNA damage
True or False:
Repair enzymes that have endonuclease activity can make cuts at the ends of the backbone
False, repair enzymes that have endonuclease activity can make cuts that are within the backbone
Define:
Thymine Dimers
A type of damage that occurs when adjacent thymines are exposed to UV light
How are thymine dimers repaired?
Photolyase + white light
Excision repair
Describe a thymine dimer
Formed under UV light, when two T bases to covalently bond together (forming a dimer)
Define:
Non-Homologous End Joining (NHEJ)
Repairs double-stranded breaks by joining blunt ends without using a template
True or False:
NHEJ is relatively precise
False, NHEJ is very sloppy as it grabs floating nucleotides and puts them back in random orders and numbers
What mutations can NHEJ result in?
Insertion, deletion, or inversion
True or False:
Only 90% of your DNA is essential coding
False, only 10% of your DNA is essential coding
What does 2% in the 10% of essential coding account for?
Protein coding
What types of mutations are there?
Substitution, deletion, insertion, and inversion
Define:
Substitution mutation
Also known as point mutation, when one base changes
Define:
Deletion mutation
When a base pair is removed