Characteristics of living organism - Essay Example

Viruses Our cells are considered alive. They have their own DNA and can replicate individually of one another. They also have a predetermined lifetime in that they exist only for a limited amount of time. Viruses are not alive. They can also exist for millions of years in a variety of types of conditions. Many scientists hypothesize that viruses were the predecessors to cells due to the fact that they share some characteristics. The structure of a virus is very simple. It usually consists of a protein coat which houses the genetic material and then proteins on the outside that allow it to interface with the cell membranes it will infect.

The genetic material can exist either as double stranded or single stranded DNA/RNA. Those that have RNA, such as HIV and Influenza, are termed retroviruses and are hard to come up with vaccinations for due to the fact that they synthesize their DNA while they are in the host cell (Beckner, Kleinsmith, Hardin, and Bertoni 99-101). Viruses have their own kind of genetic material which can be stored as DNA or as RNA. The biggest reason as to why viruses are not alive is because they cannot reproduce on their own.

They are biological machinery which requires a host. They work by injecting their foreign genetic material into the cell and taking over the cells processes. In the lytic cycle, the machinery in the cell is turned over to the control of the virus. It then begins to replicate copies of itself within the cell. After the maximum area in the cell has been taken up, the cell lyses releasing all the new viruses to infect other cells in the organism. In the lysogenic cycle, the virus integrates its own genetic material into that of the host where it replicates with the organisms genetic material until external factors cause it to become active, which after it enters in to the lytic cycle (Sadava, Heller, Hillis, and Berenbaum 343-48).

Viruses are even sometimes used in helping with gene therapy. Scientists will incorporate a missing or properly encoded human gene into the viral genome. Then they will have that virus infect improperly functioning cells in an effort to deliver the properly coded human gene. After this, the new genetic material will be integrated into the cell causing it to function properly. This is one of the main reasons why viruses cannot be considered cells in that we use them as biological machinery. Works Cited Beckner, Wayne, L Kleinsmith, J Hardin, and Gregory Bertoni.

 The World of the Cell. 7th ed. San Fransisco, CA: Pearson Education, 2009. 99-101. Print. Sadava, David, H Heller, David Hillis, and May Berenbaum. Life: The Science of Biology. 9th ed. Sutherland, MA: Sinauer Associates, 2011. 343-48. Print.