Nothing can be patented in its natural state, including native varieties of plants or animals, or anything within the human body. A customary use of a natural object cannot be patented either. A new or non-obvious use of something occurring in nature is patentable, however. It must have utility. Rube Goldberg nonsense machines are not patentable.
ESTs are fragments of genes that have been isolated by automated processes, often randomly.
The sequencing of the human genome depends largely on isolating ESTs, seeing where they overlap, and then patching them together to form entire genes. A biotechnology company that has developed a particular process for isolating ESTs can patent both the process and the ESTs it finds. The process is new and the ESTs have not been previously discovered. This satisfies the requirement of novelty. The ESTs are not obvious in the human body, only in the lab.