Which have correctly describes crossing over

There are fewer than 100 naturally occurring elements in the universe, but there are millions of different unified substances. explain how this can be true.

What factors contribute to the effect an environmental toxin has on the human body?

Do the following statements describe actin, myosin, both of the proteins or neither of the proteins? (a) contains a binding site for calcium (b) found in the i band (c) exists in a globular (g) form and a filamentous (f) form (d) contains a binding site for atp (e) is a component of the thin filament (f) is a component of the thick filament