Answer:
nucleic acid (single- or double-stranded RNA or DNA) and a protein coat, the capsid, which functions as a shell to protect the viral genome from nucleases and which during infection attaches the virion to specific receptors exposed on the prospective host cell.
Explanation:
The aortic valve prevents backward flow of blood into the left ventricle.
Spindle fibers are formed from microtubules with many accessory proteins which help guide the process of genetic division. Each spindle fiber forms during cellular division near the poles of the dividing cell. As they extend across the cell, they search for the centromere of each chromosome
