Today I’m going to talk about: Virus (life science)

Virus (life science), infectious agent found in virtually all lifeforms, including humans, animals, plants, fungi, and bacteria. Virusesconsist of genetic material DNA or RNA but not both surrounded by aprotective coating of protein, called a capsid, with or without an outerlipid envelope. Viruses are between 20 and 100 times smaller than bacteriaand hence are too small to be seen by light microscopy. Viruses are notconsidered free-living, since they cannot reproduce outside of a livingcell; they have evolved to transmit their genetic information from one cellto another for the purpose of replication. Viral replication is oftencarried out at the expense of the host: Diseases such as herpes, rabies,influenza, some cancers, poliomyelitis, and yellow fever are of viralorigin. Of the estimated 1000 to 1500 types of viruses, approximately 250cause disease in humans (over 100 of which cause the common cold), and 100infect other animals. Because viruses are programmed to carry geneticinformation into cells, they have been used to replace defective cellulargenes. Viruses are also being altered by genetic engineering to killselected cell populations, such as tumor cells. The use of geneticallyengineered viruses for medical intervention is a relatively new field, andnone of these therapies is widely available.

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