Final answer:
Guanine is the most susceptible base to oxidative stress due to its low redox potential. It is converted into 8-oxo-7,8-dihydroguanine (8-oxoG), which can mispair during DNA replication, leading to potential mutations such as G:C to T:A transversions implicated in cancer and other age-related diseases.
Step-by-step explanation:
Guanine (G) is the most susceptible base to oxidative stress because it has the lowest redox potential, making it the easiest target for oxidation by reactive oxygen species (ROS). In the presence of ROS, guanine is often converted into 8-oxo-7,8-dihydroguanine (also known as 8-oxoG). The structure of 8-oxoG includes a double-bonded oxygen added to the carbon in the six-membered ring of guanine.
The mutagenicity of the 8-oxoG lesion stems from its ability to pair with both cytosine and adenine during DNA replication. This mispairing increases the likelihood of G:C to T:A transversion mutations in the DNA sequence, which can cause errors in protein coding and lead to conditions such as cancer and age-related diseases.
Oxidative stress is a significant contributor to the aging process and various age-related diseases, including cancer, by causing permanent damage to DNA and changing genetic information. The formation of 8-oxoG is a marker of this type of cellular damage and is highly relevant in studies of carcinogenesis and the aging process.