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3. Replication and synthesis.
The entirety of the genetic material needed to produce new 
viruses is found in the viral genome. After entering a host cell, the virus degrades the nucleic acid. 
The virus then replicates its own nucleic acid and produces viral proteins using the host cell’s 
molecular machinery. Many antiviral drugs prevent viral nucleic acid replication. 
4. Assemble.
The newly created viral building blocks are put together to form new viruses. 
 
5. Release.
The assembled viruses are expelled from the cell. Typically, the host plasma 
membrane is destroyed by lytic enzymes that the phage produces late in the replication process. Phage 
release is typically all at once, resulting in rapid cell lysis. Animal viruses, on the other hand, are 
frequently released slowly or bud off from the plasma membrane. 
 
Viral diseases
For thousands of years, humans have known and feared viruses-caused diseases. Viruses 
cause diseases such as 
influenza
, 
smallpox
, 
hepatitis
, 
yellow fever
, 
polio
, 
AIDS
, and 
SARS
. Viruses 

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have also been linked to certain cancers, including leukemia. Viruses not only cause many human 
diseases, but they also cause significant losses in agriculture, forestry, and natural ecosystem 
productivity
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. 
5.2 Reading Resource #2
: Prokaryotic Diversity
Prokaryotes are present everywhere. They live on and inside other living things, and they 
cover every surface one can think of where there is enough moisture. There are more prokaryotes 
inside and on the exterior of the human body than there are human cells in the body. Some prokaryotes 
thrive in environments that are inhospitable for most other living things. Prokaryotes recycle 
nutrients, which are vital components (such as carbon and nitrogen) that are responsible for the 
evolution of new ecosystems, some of which are created by nature and others by human activity. 
Prokaryotes have existed on Earth for a very long time, long before multicellular life did. 
The advent of DNA sequencing provided immense insight into the relationships and origins 
of prokaryotes that were not possible using traditional methods of classification. A major insight 
identified two groups of prokaryotes that were found to be as different from each other as they were 
from eukaryotes. This recognition of prokaryotic diversity forced a new understanding of the 
classification of all life and brought us closer to understanding the fundamental relationships of all 
living things, including ourselves.