L3M2 – Effects of Ionizing Radiation on DNA and Chromosomes

What is a single strand break?

When one of the sugar phosphate chain side rails or strands break. This is also called a point lesion. Usually occurs in low LET radiation and can be repaired by enzymes

What is a double strand break?

Additional breaks in the sugar phosphate molecule chain. These are repairable but not as easy, and if not repaired further separation can concur in the DNA threatening the life of the cell. More commonly found from high LET radiation. It can also lead to a complete loss of a nitrogenous base

What happens after a low LET radiation passes through DNA?

Can fragment or develop a super like molecule at the end which becomes sticky and interacts with other molecules to for cross links

What are interstrand cross links?

DNA cross linking in two different DNA

What are intrastrand cross links?

DNA crosslinks in the same DNA segment

What part of mitosis is visible change caused by irradiation?

• Metaphase and anaphase 

What are aberrations caused by?

early interphase before DNA synthesis takes place. The break is a single strand of chromatin and is replicated.

How much do single strands join back to their regular configuration? What is this called?

Restitution , 95%

interstrand

attachment to other
macromolecules

intrastrand

other segments of the same
macromolecule chain

chromosome
aberration

Chromosome damage that occurs before DNA synthesis.The break is replicated in DNA synthesis and each daughter cell will inherit the damaged chromatid

chromatid
aberration

Chromosome damage that occurs after DNA synthesis.Only one daughter cell is affected

Broken-end rearrangement

grossly misshapen chromatids may be produced

Broken-end rearrangement
without visible damage to the
chromatids

Chromatid genetic material
has been rearranged, though
the chromatid appears
normal

Consequences to the Cell from
Structural Changes in the
Nucleus

1. Restitution

2. Deletion

3. .Broken-end rearrangement

4. Broken-end rearrangement without visible damage to the chromatids

If the cell hasn’t died it can recover from

sublethal radiation damage