By Itay Hod Three-year-old Leo Davies of San Anselmo loves basketball. Though “love” might not be a big enough word. Put a game on television, and he’ll sit there, completely captivated. His parents aren’t exactly sure why, and Leo can’t tell them. “Leo’s first three years of life have largely been in the hospital, in surgeries, in therapies,” said Cassie Davies, Leo’s mom. Leo was born with a rare chromosome disorder, missing genes that left hi…