5 Viruses Dna Structure
A virus is basically a gene transporter with the express purpose of infecting another cell in order to replicate. The virus consists of genetic material, either DNA or RNA, protected by a protein shell called a capsid. This capsid is typically self-assembled by proteins created by the viral genetic material. Some viruses however do assist in the construction of the capsid.
The first morphological type is the helical virus. The helical virus has a single type of protein in the shape of an enclosed tube, surrounding the genetic material, that resembles a spiral staircase. This causes the virus to be long and flexible, or short and rigid. The longer a helical virus, the more flexible it must be to prevent forces from snapping it. The length of the virus capsid is dependent on the length of the genetic material and the width of the virus depends on the length and arrangement of the proteins of the capsid.
The second morphological type is the icosahedral capsid. This symmetrical morphology causes the virus to appear spherical under low magnification but it actually contains capsomers, ring shaped structures, that are arranged in a pattern similar to a soccer ball. Capsomers may contain more proteins than the helical virus, a capsomer is constructed from five or six copies of each protein. Icosahedral capsids enclose the viral genetic material less intimately than the helical capsid. The icosahedral form was used by R. Buckminster-Fuller to create the geodesic dome.
The third morphological type is the enveloped virus. This virus, in addition to having a capsid, are able to acquire an altered form of cell membrane from an infected host cell. There are two layers to this membrane, or viral envelope. The inner membrane contains proteins coded by the virus genetic material and proteins coded by the host's genetic material, while the outer layer and any carbohydrates are strictly coded from the host DNA. The viral envelope gives viruses certain advantages over other naked viruses, the most notable of which is the protection the virus gains from the host organism. This envelope causes nearby cells to mistakenly believe the virus is a friendly cell, which results in the virus being taken into the healthy cell. However this envelope has drawbacks for the virus. Many viruses related to 5 Viruses Dna Structure with these envelopes are so dependent upon them that if the envelope is removed, the virus dies.
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