Final answer:
Biomarkers are proteins indicating specific diseases, such as CA-125 and PSA for cancers. They are also global indicators of life, potentially detectable on other planets.
Step-by-step explanation:
A biomarker is an individual protein that is uniquely produced in a diseased state and can be used as an indicator of an organism's disease or physiological state. Examples of biomarkers for various forms of cancer include CA-125 for ovarian cancer and PSA for prostate cancer. Beyond the solar system, a biomarker could be evidence of the presence of life, such as an unusual atmospheric composition that suggests biological processes.