Question

Name two major types of ionizing radiation that can cause DNA lesions. What are the two main types of lesion that ionizing radiation cause, and which type is double-strand breaks? What are four possible results of double-strand breaks?

What type of damage to DNA does aflatoxin cause? Where does it come from, and what must happen to it for it to become activated to cause DNA damage?

Answer 1

Ionizing radiation can responsible for causing DNA lesions mainly to include ultraviolet rays and high-frequency rays like X-rays. These high-energy type radiation release electrons from to generate ions that can easily break covalent bonds and affects DNA by inducing breaks in the structure, particularly, Double-Strand Breaks. Other effects include the generation of reactive oxygen species (ROS) which can oxidize proteins & lipids, and damages to DNA by producing abasic sites or single-strand breaks (SSB). The four possible results of double-strand breaks include deletions, translocations, and fusions of DNA collectively known as chromosomal rearrangements prevalent in cancerous cells. Another consequence is the occurrence of mutations in DNA.

Aflatoxins are mutagenic and carcinogenic agents that can damage DNA by forming DNA, RNA and protein adduct and also cause lipid peroxidation& oxidative damage by ROS to DNA. Aflatoxins are produced by molds like Aspergillus flavus & Aspergillus parasiticus that grow in decaying vegetation, soil, hay, & grains. Aflatoxin when metabolized to reactive epoxide called aflatoxin 8,9-epoxide is activated to the DNA damaging form. This reaction is mediated by P450 monooxygenase system. Epoxides are dangerous as they can react to form DNA adducts of aflatoxin-N⁷-guanine inducing mutations & cancer.