1 the genetic material<span> made from either </span>DNA<span> or </span>RNA<span>, long </span>molecules<span> that carry genetic information 2 a </span>protein<span> coat, called the </span>capsid<span>, which surrounds and protects the genetic material; and in some cases 3 an </span>envelope<span> of </span>lipids<span> that surrounds the protein coat when they are outside a cell. The shapes of these virus particles range from simple </span>helical<span> and </span>icosahedral<span> forms for some virus species to more complex structures for others. Most virus species have virions that are too small to be seen with an </span>optical microscope<span>. The average virion is about one one-hundredth the size of the average bacterium.</span>
