Viruses are much smaller than bacteria and consist of a single- or double-stranded nucleic acid (DNA or RNA) surrounded by a protein shell called a capsid; some viruses also have an outer envelope composed of lipids and proteins. They vary in shape. The two main classes are RNA viruses and DNA viruses.
What is the structure and shape of viruses?
In general, the shapes of viruses are classified into four groups: filamentous, isometric (or icosahedral), enveloped, and head and tail. Filamentous viruses are long and cylindrical. Many plant viruses are filamentous, including TMV (tobacco mosaic virus).
What are the four criteria that define the structure and classification of a virus?
The order of presentation of virus families and genera follows four criteria: (1) the nature of the viral nucleic acid; (2) the strandedness of the nucleic acid; (3) the use of a reverse transcription process (DNA or RNA); and (4) the positive or negative sense of gene coding on the encapsidated genome.
What are the two main structural parts of a virus?
All viruses contain nucleic acid, either DNA or RNA (but not both), and a protein coat, which encases the nucleic acid. Some viruses are also enclosed by an envelope of fat and protein molecules. In its infective form, outside the cell, a virus particle is called a virion.
What are the 2 basic shapes of viruses?
Shapes of viruses are predominantly of two kinds: rods, or filaments, so called because of the linear array of the nucleic acid and the protein subunits; and spheres, which are actually 20-sided (icosahedral) polygons. Most plant viruses are small and are either filaments or polygons, as are many bacterial viruses.
What is the classification of virus?
Classification of virus. February 4, 2019 by. Viruses are small obligate intracellular parasites, which by definition contain either a RNA or DNA genome surrounded by a protective, virus-coded protein coat. Viruses range from the structurally simple and small parvoviruses and picornaviruses to the large and complex poxviruses and herpesviruses.
What is a fungal cell type?
Fungi are eukaryotes, meaning that like parasites, their cells have a true nucleus and complex internal structures. They are most commonly found as environmentally resistant spores and molds, but can cause disease in humans in the form of yeasts.
What is a virus family?
Small viruses, e .g., hepatitis B virus or the members of th e picornavirus or parvovirus family, are families. Viruses are classified on the basis of morphology, chemical composition, and mode of replication. The viruses that different viruses whose host ranges extend from vertebrates to protozoa and from plants and fungi to bacteria.
What is the structure of a DNA virus?
A virus consists of genetic information — either DNA or RNA — coated by a protein. Accordingly, they are classified as DNA viruses and RNA viruses. The nucleic acid may be single or double stranded, circular or linear, segmented or unsegmented.
