Biological Effects Flashcards
4 phases of cell cycle:
M, G1, S, G2
Cell phase(s) where there is a gap in cell growth
G1, G2
Cell phase where there is DNA synthesis and the molecule is replicated to two molecules
S
4 phases in M phase:
Prophase
Metaphase
Anaphase
Telophase
Phase in M phase where DNA swells, takes structural form
Prophase
Phase in M phase where Chromosomes appear and line up
Metaphase
Phase in M phase where Chromosomes split
Anaphase
Phase in M phase where Chromosomes become mass of DNA
Telosphase
In ___ a second division without duplication of chromosomes occurs
Meiosis
2 categories of human sensitivity to radiation:
- organ sensitivity
- cellular radiosensitivity
Cellular radiosensitivity depends on 2 things:
- rate of proliferation (how quickly the cells mature)
- state of development of the cells (how differentiated or undifferentiated they are)
Lymphocytes, spermatogonia, erythroblasts, intestinal crypt cells are ___ radiosensitive
highly
Endothelial cells, osteoblasts, spermatids, fibroblasts have ___ radiosensitive
Intermediate
Muscle cells, nerve cells have ___ radiosensitivity
low (radioresistant)
Tissues with high radiosensitivity require __ - __ Gy to cause change in cells.
2-10
Tissues with intermediate radiosensitivity require __ - __ Gy to cause change in cells.
10-50
Tissues with low radiosensitivity require > __ Gy to cause change in cells.
50
Lymphoid, bone marrow, and gonads are ___ radiosensitive
highly
Skin, GI tract, cornea, growing bone, kidney, liver, and thyroid have ___ radiosensitivity
intermediate
Muscle, brain, and spinal cord have ___ radiosensitivity
low
Law of B andT says: Radiosensitivity of cells is ___ proportional to their reproductive activity and ___ proportional to their degree of differentiation (specialization)
directly, inversely
Less specialized cells and cells with high metabolic rate are ___ sensitive to radiation
more
LET
linear energy transfer
rate at which energy is transferred from ionizing radiation to tissue
LET
RBE
Radiobiological Effectiveness
As LET increases, RBE ___
increases
the higher the RBE, the ___ the radiosensitivity
higher
dose delivered over a period of time
Protraction
dose delivered in discrete fractions
Fractionation
OER
Oxygen Enhancement Ratio
oxygenated (oxygen present)
Aerobic
OER (oxygen enhancement ratio) has more effect with ___ LET (linear energy transfer).
low
Age sensitivity to radiation: 3 most sensitive age groups
- Unborn
- Very young (kids)
- Elderly
Recovery is ___ and ____
repair, repopulation
Interphase death means cells die before ___
replicating
Chemo given 1 hour before RT is an example of a ___, which ___ the effect of RT.
Radiosensitizer, enhances
___ mitigate the effect of RT, but doses are too toxic to use in RT.
radioprotector
Molecular Radiobiology: when radiation makes a cut in the chain
Main-Chain Scission
Molecular Radiobiology: when radiation causes two parts to join or link together at a point where they shouldn’t
Cross-Linking
Molecular Radiobiology: when radiation damages information at only the point that it hits
Point Lesion
2 types of main-chain scission:
- one side rail severed
- both side rails severed
4 radiation effects on DNA:
- cell death
- abnormal replication
- genetic abnormalities
- repair
Radiolysis of water (in Radiobilogy): Water ___ or __ an electron. Ion pairs recombine and form ___.
gains, loses, free radicals
Uncharged molecule with unpaired ____ can combine to create ___, which is __ to cells.
valence electron, Hydrogen Peroxide (H2O2), toxic
Damage due directly to radiation (DNA damage), where effect is seen at cellular level
Direct effect
Ionizing event creates molecule which damages another cell (Free radicals) and the primary effect is seen at the whole body level.
Indirect effect
___ effect usually occurs shortly after exposure and is associated with higher doses of radiation
deterministic
___ effect usually occurs very long after exposure and is associated with lower doses of radiation
stochastic
Dose response relationships have been determined using 3 ways:
- experiments
- accidental exposures
- natural exposures (background radiation in the environment i.e. Denver)
Horemesis dose response (theory/graph) says what about low doses of radiation?
it is good
favorable biological response to low exposure to that which would be toxic or harmful at large exposures
Hormesis
____ theory is used. It is considered conservative. It is not validated at ___ doses, meaning we don’t actually have any data.
linear non-threshold, low
In atomic bomb survivors, no observed increase in cancer for exposures less than ___ mSv
150
French Academy of Sciences (2005) says there is no evidence of validity of NLT model to estimate carcinogenic risks at doses less than ___ mSv
100
Spontaneous Mutations: natural background mutation rate ___ typical radiation background mutation rate by 10^6
exceeds
No biological basis for LN-T. In fact, biology suggests a ___ to low doses of radiation
benefit
- Radiation effects are ___ at large exposures in short time frame
- Small exposures, longer time effects are ___
known, less well known
Prophase
Metaphase
Anaphase
Telophase
Identify where both mitosis and meiosis are occuring.

Identify each type of DNA damage:
A: Main-Chain Scission
B: Cross-Linking
C: Point Lesion
Identify each type of DNA damage:
A: Main-chain scission - one side rail severed
B: Main-chain scission - both siderails severed
Identify each type of DNA damage:
C: Main-chain scission followed by cross-linking
D: Rung breakage – separation of bases
Identify the following chromosomes as normal or damaged, if damage what type of damage?
A: normal
B: terminal deletion
C: dicentric formation
D: ring formation
4 types of cells that are highly sensitive ot radiation:
Lymphocytes
spermatogonia
erythroblasts
intestinal crypt
4 types of cells that have intermediate radiosensitivity
Endothelial cells
osteoblasts
spermatids
fibroblasts
___ cells and ___ cells have low radiosensitivity
Muscle, nerve
3 organs with high radiosensitivity:
Lymphoid
bone marrow
gonads
7 organs with intermediate radiosensitivity:
Skin
GI tract
cornea
growing bone
kidney
liver
thyroid
3 organs that have low radiosensitivity:
Muscle
brain
spinal cord
Water gains or loses an electron. Ion pairs recombine and form free radical.
Radiolysis of water (in Radiobilogy):