Body Parts: Double-Jointedness, Hitchhiker's Thumb, and More (Lightning Bolt Books)

Can you stretch your thumb back to your arm? Is your pinkie straight or slightly bent? What determines the way your joints bend—or don't bend? Read this book to find out about how your genes affect your physical features.

Buffy Silverman is the author of 90 nonfiction books for children, featuring topics from angel Sharks to alligators, and Mars to monster trucks. Look for her nature-inspired poetry in anthologies and children's magazines, and visit her at www.buffysilverman.com