The band of a muscle fibril that contains only actin is the

1. A muscle fibril shows alternating light and dark bands. 2. The light band contains actin and is called the I-band or isotropic band. 3. The dark band contains myosin and is called the A-band or anisotropic band. 4. So actin alone marks the I-band. _Source: syllabus Biology Ch17 'Locomotion and Movement'_