Microbiology

Microbiology Study Guide

lacked genes are added and the cells are altered, they are then replaced in the patient so that the genetic codes for the proteins are replaced. • DNA fingerprinting: Genetic engineering has also made its way from the medicine to non- medicine line. It is possible to identify different organisms uniquely by matching the DNA molecules with the help of DNA probes and retrieval techniques. These techniques are mostly used in forensic science. • DNA and agriculture: The cultivation of plants is possible with the help of genetic engineering. In the field of agriculture, it has now become possible to insert genes and then cultivate the plants as to provide mature plants. The species of the bacterium Agrobacterium tumefaciens is one of the most common genes used through the plasmids of the bacterium to detect for induction of tumor in plants. It becomes easy to extract the tumor inducing genes and obtain a plasmid that unites with the plant cell without causing any harm. 2.5 Viruses Viruses are genetic elements that have no cellular walls and make use of a living host cell in order to metabolize and replicate themselves. These are ultra-microscopic particles that contain proteins around the nucleic acid or macro-molecular substances. When the viruses do not enter the host cells, they are termed as virion. Structure Viruses can be divided into categories based on their structure: viruses containing ribonucleic acid (RNA) and viruses containing deoxyribonucleic acid (DNA). The genome of the virus contains the nucleic acid, which can have one or two strands. It can have either a linear or closed loop, and have the capability to occur in continuous form or segments. This genome is surrounded by capsid, which is a coat of protein formed from the molecules of proteins defined as capsomeres . The nucleic acid is surrounded by the capsomeres, which are arranged in a repetitive pattern. These capsomeres can either have the same characteristics or may contain different chemical features. When the genome and capsid are combined, it is referred to as nucleocapsid . Some of the viruses contain envelopes that resemble the structure of a membrane. This envelope is generated only when the virus replicates itself after attaching to the host cell and encloses the nucleocapsid. One of the unique features of this envelope is that it contains proteins that are specific to viruses. Some examples of envelope viruses are chickenpox, herpes simplex, and mononucleosis. There are symmetrical patterns for the virus’s nucleocapsids. Some of these patterns are helical symmetry in which the nucleocapsid is tied like a tightly coiled spiral (e.g., the rabies virus); some are icosahedral symmetry, since the shape of the virus is that of icosahedrons. Some viruses also presume a lipid bi-layer as their envelope, which contains glycoproteins. The structure of these viruses is

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