long palmar muscle: Leslie has a muscle in her forearm which is called the long palmar muscle. She knows that she has this muscle because the can feel its tendon in her wrist. Leslie has a twin brother, Louis, who does not possess the long palmar muscle. Leslie's parents also lack the long palmar muscle. Leslie is married to a man, Jim, who has the long palmar muscle. Their first two children are identical twin boys who also have the long palmar muscle. What is the most probable mode of inheritance for the long palmar muscle?