Viruses nucleic acid content

Nucleic acid content 8 Multiplication of human viruses... 

DNA vaccines Direct injection of nucleic acid contents HIV, malaria, influenza, hepatitis B virus, cancer... 

All forms of life—animal, plant and even bacterial—are susceptible to infection by viruses. Three main properties distinguish viruses from their various host cells size, nucleic acid content and metabolic capabilities. 

Based on the nucleic-acid content of the infectious virus, and the nucleic-acid product of the first replication phase, most common animal viruses can be classified into four groups. These four modes of replication are DNA DNA, RNA RNA, DNA RNA, and RNA DNA. 

There has been a steady accumulation of evidence to support the Idea that the most Important damage to a cell that leads to mitotic failure Is a macromolecular lesion of DMA in the nucleoprotein system.Cellular radlosensltlvlty In 120 diverse organisms ranging from viruses to higher plants and animals was a direct function of the chromosome volume and nucleic acid content. In the Intact cell of bacteria, protection by thiols appears to be protection of a functional repair mechanism rather than prevention of DNA degradation, but the need for more information about damage to DMA remains moot. 

The abnormal deposits found in the brains of CJD victims consist of an abnormal isoform of PrP. Prion protein is normally found in cells. Detailed structural studies show that normal cellular PrP (PrP ) is a soluble protein whose conformation is rich in a-helices with very little P-sheet. The PrP protein extracted from the brains of CJD victims (i.e., PrP ) is identical in primary amino acid sequence to the normal PrP (PrP ). However, PrP has a much greater content of P-sheet conformation with little a-helical structure. Thus PrP is neurotoxic because of its three-dimensional structure. When the prion protein is predominantly in an a-helical conformation it is nontoxic when the prion protein is predominantly in a P-sheet conformation, it kills neurons. The prion protein is thus made neurotoxic not by its amino acid composition but by its conformation. This concept is both fascinating and terrifying. Prion diseases are transmissible thus prions are infectious agents. However, prions are not like bacteria or viruses, or other infectious microbes—they are simply protein molecules. Prions are not microbes with cell membranes and nucleic acids they are not living things. Indeed, prions are not even infectious molecules, they are infectious molecular shapes. 

Yet again the conclusion can be drawn that all single-stranded RNA viruses are subject to similar restrictions with regard to information content. In nature there are no (single-stranded) RNA viruses whose replicative unit contains more than the order of 104 nucleotides. All larger viruses possess double-stranded nucleic acids or are composed of several... 

Biomembranes are large flexible sheets that serve as the boundaries of cells and their intracellular organelles and form the outer surfaces of some viruses. Membranes literally define what is a cell (the outer membrane and the contents within the membrane) and what is not (the extracellular space outside the membrane). Unlike the proteins, nucleic acids, and polysaccharides, membranes are assembled by the noncovalent association of their component building blocks. 

A membrane in a cell wall fulfills a number of functions. It acts as a barrier to prevent the contents of a cell from dispersing and also to exclude external agents such as viruses. The membrane, however, does not have a purely passive role. It also enables the transport of ions and chemicals such as proteins, sugars and nucleic acids into and out of the cell via the membrane proteins. Membranes are important not only as the external cell wall, but also within the cell of eukaryotes (plants and animals, but not most bacteria) where they subdivide the cell into compartments with different functions. 

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