Gregor Mendel did not know about chromosomes. He conducted his groundbreaking work on inheritance in the mid-1800s, long before chromosomes were discovered.

Chromosomes were first observed in the late 1800s, and their role in inheritance wasn't fully understood until the early 1900s, after Mendel's work.

Mendel's contribution was primarily focused on understanding the patterns of inheritance of traits in pea plants, without the knowledge of the physical structures involved (chromosomes).