RB Astro topic 2 Flashcards
What is the primary target of radiation damage in cells?
Nuclear DNA
Nuclear DNA is considered the most important target for radiation damage due to its structure and the consequences of damage.
What are the possible outcomes of DNA damage due to ionizing radiation?
- DNA repair
- DNA mutations
- Cell death
- Acute radiation toxicities
- Late tissue toxicities
- Developmental effects in the fetus
True or False: Mitochondrial DNA is more important than nuclear DNA in terms of radiation damage.
False
Mitochondrial DNA is less important because it has multiple copies and damage to a few does not significantly impact cell function.
What is the most common type of DNA damage caused by radiation?
Base damage
Base damage is easily repaired and is the most frequent type of damage encountered.
What are the two types of DNA repair pathways discussed?
- Homologous recombination (error-free)
- Non-homologous end joining (error-prone)
Fill in the blank: The repair of single strand breaks is typically carried out by _______.
Base excision repair
What is considered a double strand break in DNA?
Two single strand breaks that are close to each other
What is a multi-damage site (MDS)?
A combination of damage within a 20 base size or a 10 nanometer diameter volume of chromatin
MDS can include various types of damage like single strand breaks, double strand breaks, and base damage.
What is the consequence of a double strand break in DNA?
Loss of genetic material and potential mutations
Double strand breaks can lead to errors in DNA repair processes, resulting in mutations.
What is the term for damage that occurs when DNA strands do not join together correctly after a double strand break?
Illegitimate recombination
This process can lead to significant mutations and loss of protein function.
What type of radiation is most likely to produce complex lesions?
High LET radiation
Complex lesions can also occur from low LET radiation but are more commonly associated with high LET radiation.
What happens during homologous recombination repair?
A double strand break uses a duplicate of its chromosome to repair itself.
What are the typical phases of the cell cycle where most DNA repairs occur?
- G0
- G1
- Early S phase
These phases are less favorable for homologous recombination since duplication of the chromosome occurs in late S and G2 phase.
What is the relationship between ionizing radiation and free radicals?
Ionizing radiation can lead to free radical formation, which can further damage DNA.
What is the significance of clustered lesions in radiation damage?
They involve multiple types of damage in a small area, complicating the repair process.
What is the D0 dose for mammalian cells and its expected damage outcomes?
1 to 2 gray
At this dose, expect over 1,000 base damage lesions, 1,000 single strand breaks, and around 40 double strand breaks.
True or False: Single strand breaks are more damaging than double strand breaks.
False
Single strand breaks are easier to repair and less harmful than double strand breaks.
What is the expected damage from radiation exposure?
1,000 to 2,000 damage bases, 1,000 single strand breaks, 40 double strand breaks
What does a D0 dose refer to in radiation exposure?
One gray (but not exactly one gray)
What types of damage are primarily caused by gamma rays and x-rays?
- Single base damage
- Single strand breaks
- Double strand breaks
What types of damage are primarily caused by UV radiation?
- TT dimers
- Cyclobutylperminine dimers
What is the difference between alkaline and neutral solutions in measuring DNA strand breaks?
Alkaline detects single strand breaks and double strand breaks; neutral detects only double strand breaks
What is the purpose of the filter elution assay?
To distinguish between single strand breaks and double strand breaks
How does the comet assay work?
Measures broken DNA by observing the formation of a comet tail when an electric current is applied
