New Studies Ask, “What Is a Gene?”

The early achievements of molecular biology researchers might have spoiled us. The first identified “molecular disease,” sickle cell anemia, involved a single mutation in the globin gene. Then came the central dogma of molecular biology: DNA makes messenger RNA (mRNA), and mRNA makes protein. Therefore, the DNA segment that coded for a protein was a gene. Diseases would result from structural abnormalities in genes.

However, we soon realized that, unlike sickle cell anemia, most diseases probably didn't derive from a structural abnormality in a single gene, but from the combined effects of abnormalities in multiple genes. Members of the Human Genome Project set out to determine the sequence of every gene — every stretch of DNA that coded for…