Plants grown from runners and leaf cuttings have the same traits as the parent plant. Plants grown from seeds can vary from the parent plants in many ways. Why can this happen?

Explanation:

Plants produced from asexual reproduction are the result of mitosis, so they are genetically identical.

Viruses need to be inside a living thing (of course the living thing has to have the right temperature which most living things do) . When they're inside a living thing they start injecting the host's cells with its DNA in order to make more copies of itself which allows the virus to spread. So basically viruses need to be inside something living.