Several years ago, scientists discovered a mutation in zebrafish larvae that prevented the absorption of lipids from dietary fat. Larvae carrying this mutation died shortly after they hatched because all cells need fat to carry out their normal functions. More recent studies have determined that the mutation leading to this disorder occurs in a single gene on chromosome 10. When a normal gene is inserted into embryos carrying the mutation, these fish are able to process fats normally when they hatch. To discover more about the gene's function, researchers examined and compared cells from normal and mutant fish larvae under a microscope. A major difference was noticed in the intestinal cells. The Golgi apparatus in the intestinal cells of mutant larvae is much larger than those of normal larvae. As the Golgi apparatus processes fats and proteins, the lipids become trapped, resulting in the abnormally large size of the organelle. Assuming that the digestive system of zebrafish works like that of a human, which portion of the digestive tract is specialized for absorption of the nutrients