what is target theory
explains hownand why cells become damaged or die when expo to ionizing rad . DNA is the target molecule and can be damaged if it has been hit. these hits can be direct or indirect effects
what is the probability of a low LET rad to hit
low bc large distances between events
what is the probability of a high LET rad to hit
higher bc it can hit directly
if oxygen is present with low LET rad, what is the probability of it to hit
higher bc free radicals are formed
what is a single strand break
hit on one strand of DNA where the phosphate bond on one strand is disturbed.
called a point lesion and happens often w low LET
can be repaired by enzymes and reverse damage
what is a double strand break
both sides of a strand of DNA are disrupted and may lead to mutation, change, or loss of nitrogen base.
common w high LET
could be repaired , but unlikely
what is a double strand break in the same rung of DNA
results in the DNA breaking in half and making 2 separate chromosomes. each new chrom will contain half of gen info and will pass down incorrect gen into
they could recombine or cause mutation
results in impaired finction or cell death of daughter cell
what is mutation
result from high LET, it alterates the nitro base sequence and can cause the passing o of incorrect gen info to daughter cells
what are covalent cross links
chem unions created between 2 atoms by sharing of one or more electrons causing the mix of genetic material . it causes molecules to want to attach to other macromolecules (interstrand, same mole) or other segments if the same macro chain (intrastrand, diff mole)
caused by high LET direct hit or low LET indirect hit
can be fatal if not repaired
when changes to DNA happens, what shows it
chromosomes
where do radiation induced chromosome breaks occur
occur in somatic and repro cells
as a result of radiation, what is a chromosomal fragment
produced from chrom breaking. both ends are active and want to adhere to other things. they can rejoin w each other, create aberrations (fail to rejoin), or join to other broke ends and create new chroms
what is a chromosome aberration
When chromosome damage occurs before DNA synthesis causing a break in a single strand chromatin. The break will be replicated in DNA synth and be inherited by each daughter cell
what is a chromatid aberration
only one chromatid of a pair gets broken and only one daughter cell is affected
when are cytogenetic effects/ chromosome damage most likely to happen
after high dose fluroscopy procedures
what is a single hit chromosome aberration
occurs w low dose of rad
causes structural damage to a chrom where it can either rejoin and go back to normal or join a diff chrom and be messed up
what does a chrom hit represent
severe damage to DNA
what are multi hit chromosome aberrations
a single chrom is hit multiple times causing it to have multiple breaks and form a ring shape or be dicentric (multiple centre points)
happens w high LET
what is the more significant aberration? why?
multi hit aberration
because it rearranges gen into changing a cells function or can be lost completely.
what is restitution
breaks in chroms rejoin w/o vis damage
what is deletion
part of chrom is lost in next ccell div causing cell mutation
this creates acentric fragment
what is broken-end rearrangement
a misshapen chrom is produced resulting in cell mutation or death.
can be shaped in a ring, dicentric, or anaphase bridge
what is broken end rearrangement w/o vis damage to chromotid
chrom gen material has been rearranged but it appears to be noramal, this is called translocations
results in cell mutation
list the structural changes casued by ion rad
-single strand break in 1 chrom
-single strand break in 1 chromatid
-single strand break in seperate chroms
-multi break in 1 chrom
-multi break in 1 chromatid
-chrom stickiness or clumping to gether
