The term "virus" is derived from the Latin word forposition, or slime. It was originally a
The term "virus" is derived from the Latin word for
position, or slime. It was originally applied to the noxious
stench emanating from swamps that was thought to cause a
variety of disease in the centuries before microbes were S1.______
discovered and specifically linked to illness. But it was S2.______
until almost the end of the nineteenth century that a true
virus was proven to be the reason of a disease. S3.______
The nature of viruses made them impossible to detect
for many years, even after bacteria had been discovered and
studied. Not only are viruses too small to be seen with a
light microscope, they also cannot be detected through their S4.______
biological activity, except as it occurs in conjunction with
other organisms. In fact, viruses show no traces of biological
activity by themselves. Unlike bacteria, they are not living
agents in the strictest way. Viruses are very simple pieces S5.______
of organic material composing only of nucleic acid, either S6.______
DNA or RNA, enclosed with a coat of protein made up of S7.______
simple structural units. (Some viruses also contain
carbohydrates and lipid.) They are parasites require S8.______
human, animal, or plant cells to live. The virus replicates
by attaching to a cell and inject its nucleic acid; once S9.______
inside the cell, the DNA or RNA that contains the virus'
genetic information takes on the cell's biological machinery, S10.______
and the cell begins to manufacture virtual proteins rather
than its own.
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