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7 Cards in this Set

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Parvoviruses
These are very small (22 nm in diameter), naked icosahedral viruses with single-stranded linear DNA. There are two types of parvoviruses: defective and nondefective. The defective parvoviruses, e.g., adeno-associated virus, require a helper virus for replication. The DNA of defective parvoviruses is unusual because plus-strand DNA and minus-strand DNA are carried in separate particles. The nondefective parvoviruses are best illustrated by B19 virus, which is associated with aplastic crises in sickle cell anemia patients and with erythema infectiosum—an innocuous childhood disease characterized by a "slapped-cheeks" rash.
Polyomaviruses
These are naked icosahedral viruses (45 nm in diameter) with double-stranded circular supercoiled DNA. Two human polyomaviruses are JC virus, isolated from patients with progressive multifocal leukoencephalopathy, and BK virus, isolated from the urine of immunosuppressed kidney transplant patients. Polyomavirus and simian vacuolating virus 40 (SV40 virus) are polyomaviruses of mice and monkeys, respectively, which induce malignant tumors in a variety of species.
Papillomaviruses
Papillomaviruses are naked icosahedral viruses (55 nm in diameter) with double-stranded supercoiled DNA. The human pathogen in the family is human papilloma virus (HPV). It causes papillomas (warts) of many body sites and certain strains cause carcinoma of the cervix. Many animal species are infected by papilloma viruses but those viruses are species-specific and do not infect humans.
Adenoviruses
These are naked icosahedral viruses (75 nm in diameter) with double-stranded linear DNA. They cause pharyngitis, upper and lower respiratory tract disease, and a variety of other less common infections. There are at least 40 antigenic types, some of which cause sarcomas in animals but no tumors in humans.
Hepadnaviruses
These are double-shelled viruses (42 nm in diameter) with an icosahedral capsid covered by an envelope. The DNA is a double-stranded circle that is unusual because the complete strand is not a covalently closed circle and the other strand is missing approximately 25% of its length. Hepatitis B virus is the human pathogen in this family.
Herpesviruses
These are enveloped viruses (100 nm in diameter) with an icosahedral nucleocapsid and double-stranded linear DNA. They are noted for causing latent infections. The five important human pathogens are herpes simplex virus types 1 and 2, varicella-zoster virus, cytomegalovirus, and Epstein-Barr virus (the cause of infectious mononucleosis).
PoxViruses
These are the largest viruses, with a bricklike shape, an envelope with an unusual appearance, and a complex capsid symmetry. They are named for the skin lesions, or "pocks," that they cause. Smallpox virus and molluscum contagiosum virus are the two important members.