How does the written description requirement apply to genus claims?

This page is an FAQ based on guidance from the Manual of Patent Examining Procedure. It is provided as guidance, with links to the ground truth sources. This is information only: it is not legal advice.

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.