Viruses are without doubt the smallest organisms on the planet. They have a basic design, which consists of a protein capsule containing RNA or DNA (Many viruses carry there genetic information in RNA instead of DNA). This is an example of a bacteriophage:
Because most viruses adapt flawlessly to their host cell, virus structures varies greatly. But there are a few characteristics that viruses share. All viruses have a capsid, which consists of protein and glycoprotein and is where the genetic material is stored. Capsid construction varies among viruses as they form impeccably to fit their host organism. Although virus detail varies with each host cell, all viruses undergo the same steps for replication These are: 1) attachment; 2) penetration; 3) uncoating; 4) replication; 5) assembly; 6) release. As shown in Figure 1.1, the virus must first attach itself to the host cell. Then it penetrates the cell and fills it with DNA or RNA and therefore takes control of the cell.
Then the genetic material must be uncoated to make it available to the cell's replication machinery. Shortly after the cell begins the process of replicating the virus cell and assembling it and therefore the process is complete. Depending upon the phage, the nucleic acid can be either DNA or RNA but not both and it can exist in various forms. The nucleic acids of phages often contain unusual bases. The T4 is among the largest phages, which is approximately 200nm long and 80-100nm wide. The replication process of viruses is figure 23.2a.
The word Virus is from Latin meaning poison and other noxious things. It was first used in the English language in 1392 and its meaning "agent that causes infectious disease" is first recorded in 1728, before the discovery of viruses by the Russian...