The sarcomere shortens when the myosin heads of the thick filaments, in a cocked position, form cross bridges with the actin molecules in thin filaments. this activity will test your understanding of the steps that occur in one complete cross bridge cycle. place the steps that occur during a single cross bridge cycle in the correct order from left to right.

Here are the steps;

step 1. The activated myosin head binds to actin, forming a cross bridge.

Step 2. ADP is released and myosin slides the thin filament toward the center of the sarcomere.

step 3. ATP binds to the myosin head and detaches it from actin

step 4. ATP is hydrolyzed to ADP and P(i) and the energy released re-elevates the myosin head.

"1. it should be, it has been for about 20 years, and it's really not much different in the end than breeding animals to have particular traits. there are always concerns about genetically engineered animals/plants affecting the environment in unexpected negative ways, but i can't think of an example where the fears didn't turn out to be baseless.  

first, as you point out, it would be a great advance in pharmacology, to be able to tailor drugs and their doses to me. the pros involve better medical treatment. the cons involve privacy issues like insurance companies denying coverage to people with genetic risk factors. looking at dna markers wouldn't affect the frequency of genetic diseases, but it would allow detection of them earlier. and ok, actually i suppose that if people used this information to avoid having children with genetic diseases, some might decrease in frequency."