can anybody give me an example of a 'biological marker' compound and describe its precursor?

Answer 1

In medicine, a biomarker is an indicator of a particular disease state or a particular state of an organism.

In the past, biomarkers were primarily physiological indicators such as blood pressure or heart rate. More recently, biomarker is becoming a synonym for molecular biomarker, such as elevated prostate specific antigen as a molecular biomarker for prostate cancer. Biomarkers also cover the use of molecular indicators of environmental exposure in epidemiologic studies such as human papilloma virus or certain markers of tobacco exposure such as 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK).

4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (abbreviated NNK) is a nitrosamine present in tobacco that is a potent procarcinogen. It is activated by CYP2A6. It is a biomarker of exposure to cigarette smoke