Answer: The calcium ion binds to troponin, and this slides the tropomyosin rods away from the binding sites.
Explanation:
 Contraction and relaxation of muscle cells brings about movements of the body. The contractile myofilament called sarcomeres are bounded at each end by a dense stripe called the Z - line, to which the myosin fibres are attached, and lying in the middle of the sarcomere are the actin filaments, overlapping with the myosin.
When action potential spreads from the nerve along the sarcolemma (muscle cell membrane), it penetrates deep into the muscle cell through the sarcoplasm (cytoplasm of muscle cell), and releases CALCIUM from the intracellular stores.CALCIUM triggers the binding of myosin to the actin filament next to it forming CROSS BRIDGES. 
 
For this to occur, ACTIN BINDING SITE has to be made available. TROPOMYOSIN is a protein that winds around the chains of the actin filament and covers the myosin-binding sites to prevent actin from binding to myosin. The first step in the process of contraction is for calcium ions to bind to troponin so that tropomyosin can slide away from the binding sites on the actin strands.
 
        
             
        
        
        
I also believe the answer is A.
        
             
        
        
        
<em>Use a punnet square to solve the problem.</em>
<u>RG Rg rG rg  </u>
<u>rg RG Rg rG rg  </u>
<u>rg RG Rg rG rg  </u>
<u>rg RG Rg rG rg  </u>
<u>rg RG Rg rG rg</u> 
A) Crossing - over
 
        
             
        
        
        
Answer:
Propofol (another name Diprivan) can be used for Diana's surgery. It is a sedative or anesthesia commonly used for children and adults. Studies show that there were no significant differences in dose requirements based on sex or age, except for the too elderly.  The difference in dosing considering different body weights were not statistically significant also.  The same dose is safe 
( 0.1-0.15 mg/kg/min IV for 3-5 min) for Diana, the 210 lb man or a 10-year-old girl. However, the dose was higher in patients with bradycardia and hypotension.