Quick questions on Causes of mutation: physical, chemical and biological mutagens: HSC Biology Module 6

These deliver energy that physically damages DNA.

These are living agents or biological molecules that cause mutations.

<!-- Diagram: classification tree grouping mutagens into physical (electromagnetic radiation), chemical and biological with named examples | reviewed 2026-06-28 --> <svg class="fig" viewBox="0 0 440 470" role="img" aria-labelledby="grp-t grp-d"> <title id="grp-t">Classification of mutagens into three groups - physical/electromagnetic radiation, chemical, and biological - each with named examples</title> <desc id="grp-d">A tree diagram. A top box labelled mutagens branches down to three coloured group boxes. The first, physical (electromagnetic radiation), lists UV radiation and X-rays and gamma rays. The second, chemical, lists base analogues, alkylating agents, intercalators and deaminating agents.

Non-ionising, short-wavelength light in the UV-B and UV-C bands. UV photons are absorbed by adjacent pyrimidine bases (especially thymine) on the same strand, causing them to covalently bond as a thymine dimer (a pyrimidine dimer). The dimer distorts the double helix.

Molecules structurally similar to normal bases that are incorporated during replication and mis-pair. Example: 5-bromouracil resembles thymine but pairs with guanine, producing T to C transitions.

Some viruses insert their DNA (or a reverse-transcribed DNA copy of their RNA) into the host genome. The insertion can disrupt a host gene or activate a nearby proto-oncogene. Example: human papillomavirus (HPV) integrates near tumour suppressor genes and causes cervical cancer.

DNA sequences that move within the genome, sometimes inserting into and disrupting other genes. They were discovered by Barbara McClintock in maize. Transposons are responsible for many spontaneous mutations in eukaryotes.

Generated as by-products of normal aerobic metabolism. Oxidise guanine to 8-oxo-guanine, which mis-pairs with adenine and fixes a G to T transversion. These are responsible for much of the spontaneous mutation rate.

"Including but not limited to" signals NESA wants breadth: give at least one physical, one chemical and one biological mutagen, each with a distinct mechanism.

"Outline" wants brief points; "explain" wants the mechanism; "compare" wants the same features for both agents; "evaluate / assess" wants a justified judgement (e.g. UV versus ionising risk for Australians).

Thymine dimer (UV), double-strand break (gamma), 5-bromouracil (analogue), mustard gas (alkylating), acridine orange (intercalator), HPV (virus), transposon, ROS. Precise terms lift a Band 4 answer to Band 6.