Genes are part of chromosomes and code for protein production in all animals.
In this case, the protein produced was named leptin from the Greek leptos, meaning thin. In these genetically obese mice, mutations in the ob gene results in a total lack of leptin production leading to severe obesity. When leptin is administered to these mice, the mice decrease their eating, their metabolic rate increases, and they lose a significant amount of weight. The obvious question was whether a similar effect would be found in humans. In a study by Considine, et.