Radiation Effects

Deterministic

Stochastic

Threshold

A specific dose is needed to achieve response

Non-threshold

any dose produces a response

Linear

Response is proportional to dose

Non-linear

Response is not proportional to dose

Main-chain scission, cross-linking, and point lesions

When macromolecules are irradiated, 3 major effects occur:

Main-Chain Scission

breakage of the backbone of the long-chain macromolecule

Main-Chain Scission

Reduction into many smaller molecules (still considered as macromolecule)

Cross-Linking

Spurlike structures that extend off the main chain

Cross-Linking

Side structures that behave like sticky substance on the end and attach neighboring macromolecule or another segment of the molecule

Point Lesion

Result in disruption of single chemical bonds

Point Lesion

Are not detectable but can cause minor modification which in turn can cause malfunction in the cell

Main-Chain Scission with only one side rail severed

Radiation response of DNA: Easier to repair and is rarely lethal

Main-chain Scission with both side rail severed

Radiation response of DNA: more difficult to repair; causing significant structural change and high probability of malfunction or cell death

Change in or loss of a base

Radiation response of DNA: May not be reversible and can cause point mutations

Point mutations

Change in or loss of a base may not be reversible and can cause ...

- Point Mutation

- Chromosomal Aberrations

2 forms of Genetic Mutation:

Point mutation

- an alteration that occurs in the DNA base sequence of a gene

Point mutation

- Involves a single gene alteration

- small scale

Chromosomal Aberration

- An alteration in the structure of the chromosome of the organism

Chromosomal Aberrations

- involves many gene alterations

- larger scale

Chromosomal aberrations

Are structural changes to the chromosome after irradiation

aberrations, lesions, or anomalies

Chromosomal aberrations can be called ...

Karyotype

Is a chromosome map used for cytogenetic analysis of chromosomes

Photomicrographs

... are taken during metaphase that demonstrates each chromosome separately

Metaphase

Photomicrographs are taken during ... that demonstrates each chromosome separately

1. Single-Hit Chromosomal Aberration

2. Multi-Hit Chromosomal Aberration

2 forms of Chromosomal Aberrations:

Chromatid deletion

Single-Hit Chromosomal Aberration: If irradiation occurs in G1, a breakage in the chromosome will occur, termed as ...

Ring chromosome

Multi-Hit Chromosomal Aberration: if irradiation occurs in G1, if two hits occur on one chromatid, a ... will be produced

Reciprocal Translocation

Are multi-hit chromosomal aberrations. If chromosomes experience this type of alteration, they do not lose any genetic material but instead the genes become rearranged. This results in all genetic codes being available, but sequenced incorrectly

Chromosomal aberration

Chromosomal damage that occurs before DNA synthesis is known as ...

Chromatid aberration

Chromosomal damage that occurs after DNA synthesis is known as ...

1. It can be delayed from going through division

2. It can die before it divides

3. It can die when attempting mitosis

One of the three things can happen to a cell after irradiation:

Mitotic delay

- Dose dependent response

- It is the temporary postponement of cell division after irradiation

G2

Cells under mitosis during time of irradiation completes division while those under ... are delayed to avoid catastrophic mitosis

Interphase death

- Death before the cell enters mitosis

- Rapid cell death

- Occurs even before the cell tries to divide

Apoptosis

- comes from the Greek term, "falling off"

- programmed self-destruction

Mitotic death

- Death during/after the cell enters mitosis

- Delayed cell death

- Misrepair of DNA and Errors accumulate

Reproductive death

Mitotic death aka ...