Does the human DNA contain information that could, combined with other data, tell what kinds of chemicals will their digestive system process or not? For instance, there are people that have hereditary fructose intolerance (not to be confused with fructose malabsorption). Is such a lack of an enzyme discoverable through the human DNA? To be more precise in the question, does the DNA contain information defining what enzymes will one human have, be deficient, or lack completely? Are DNA and enzymes related?