The written description requirement for genus claims is particularly important and often challenging. MPEP 2304.02(d) states: "For generic claims, the genus can be adequately described if the disclosure presents a sufficient number of representative species that encompass the genus. If the genus has substantial variance, the disclosure must describe a sufficient variety of species to reflect the variation within that genus." This means that for broad genus claims, the specification must provide enough specific examples or a clear description of structural features common to all members of the genus. The description should allow a person skilled in the art to recognize that the inventor possessed the full scope of the claimed genus, not just a few species within it. To learn more: genus claims written description representative species patent specification