Dark bands of muscle fibres are made of .............. Protein while light bands of muscle fibres are made of ................

Explanation

To answer the question regarding the composition of dark and light bands of muscle fibers, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Structure of Muscle Fibers**: Muscle fibers are composed of repeating units called sarcomeres, which contain both light and dark bands.

2. **Identify the Light Band**: The light band in a sarcomere is known as the I band. This band is isotropic and primarily consists of thin filaments.

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