Answer:
Because virus are just sticking into the human
cell membranes
Answer:
Virus are small infectious particles which act as intracellular parasites. They are considered non-living when they are present outside their host because they show no metabolism outside.
They do not have even cellular level of organization and are basically just packages of nucleic acid and protein. Still, virus have some important features which are common with cell-based life like the presence of nucleic acid as their genetic material.
Apart from the presence of genetic material they also have the ability to evolve like the cell-based life. This evolution allows them to be selected naturally and produce more offspring.
A sugar phosphate backbone joins the nucleotide in a DNA sequence. A double helix has TWO backbones.
