Biological markers refer to a broad range of objective tests or measures that allow researchers to capture what is going on in an organism or cell at a given moment. They can be used to measure the presence or progress of a disease or condition. They can also be used to see how the body responds to a treatment for a disease or condition. Enzymes are called biological markers because analyzing specific enzyme activity in the body can help in the diagnosis of a variety of inherited diseases or conditions. Enzymes typically become less efficient or stop working altogether as a result of these genetic conditions.