A molecular biologist is a scientist who specializes in studying the structure and function of genes, as well as their role in the development and reproduction of living organisms. They use techniques such as DNA sequencing, gene cloning, and protein expression to understand how genetic information is stored, transmitted, and used by cells. Molecular biologists often work with microorganisms like bacteria or viruses, but they may also study the genetics of plants, animals, or humans. Their research has important applications in fields such as medicine, agriculture, and biotechnology.