DNA AND RNA VIRUSES
TABLE OF CONTENTS
Introduction
Classification of Viruses
Diseases caused by DNA viruses
Introduction
Viruses infect all cellular life forms: eukaryotes (vertebrate animals, invertebrate
animals, plants, fungi) and prokaryotes (bacteria and archaea).
Viruses are important agents of many human diseases, ranging from the trivial (e.g.
common colds) to the lethal (e.g. rabies), and viruses also play roles in the
development of several types of cancer.
There are four possibilities for a virus genome: double-stranded DNA, single-
stranded DNA,double-stranded RNA, single-stranded RNA1.
Classification
Depending on the type of nucleic acids viruses possess, they are classified into two
groups: deoxyriboviruses, which contain DNA (DNA virus) and riboviruses, which
contain RNA (RNA virus)2.
DNA viruses associated with human diseases are divided into six families.
The RNA viruses associated with human diseases are classified into at least 13
families.
DNA viruses1
Adenoviridae:
1. The members of the family Adenoviridae are medium-sized viruses measuring 20–90
nm in size.
2. These viruses are nonenveloped, icosahedral viruses with 252 capsomeres.
Poxviridae:
1. These are large-sized, brick-shaped viruses.
2. They have a complex structure with a core containing a single linear molecule of
double stranded DNA genome.
3. The pox viruses are associated with skin lesions.
4. The viral components are synthesized and assembled in the cytoplasm of infected
host cells.
Herpesviridae:
1. These are medium-sized icosahedral nucleocapsids viruses containing 162
capsomeres.
2. They are enveloped viruses containing linear, double-stranded DNA.
3. They are named after spreading appearance of cold sores.
4. The viruses multiply in the nucleus of the host cells.
Papovaviridae
1. These are small viruses containing double-stranded DNA with 72 capsomeres.
2. They are nonenveloped viruses.
3. They replicate in the nucleus of host cell along with host cell chromosome.
4. This may cause host cells to proliferate, resulting in a tumor.
Hepadnaviridae
TABLE OF CONTENTS
Introduction
Classification of Viruses
Diseases caused by DNA viruses
Introduction
Viruses infect all cellular life forms: eukaryotes (vertebrate animals, invertebrate
animals, plants, fungi) and prokaryotes (bacteria and archaea).
Viruses are important agents of many human diseases, ranging from the trivial (e.g.
common colds) to the lethal (e.g. rabies), and viruses also play roles in the
development of several types of cancer.
There are four possibilities for a virus genome: double-stranded DNA, single-
stranded DNA,double-stranded RNA, single-stranded RNA1.
Classification
Depending on the type of nucleic acids viruses possess, they are classified into two
groups: deoxyriboviruses, which contain DNA (DNA virus) and riboviruses, which
contain RNA (RNA virus)2.
DNA viruses associated with human diseases are divided into six families.
The RNA viruses associated with human diseases are classified into at least 13
families.
DNA viruses1
Adenoviridae:
1. The members of the family Adenoviridae are medium-sized viruses measuring 20–90
nm in size.
2. These viruses are nonenveloped, icosahedral viruses with 252 capsomeres.
Poxviridae:
1. These are large-sized, brick-shaped viruses.
2. They have a complex structure with a core containing a single linear molecule of
double stranded DNA genome.
3. The pox viruses are associated with skin lesions.
4. The viral components are synthesized and assembled in the cytoplasm of infected
host cells.
Herpesviridae:
1. These are medium-sized icosahedral nucleocapsids viruses containing 162
capsomeres.
2. They are enveloped viruses containing linear, double-stranded DNA.
3. They are named after spreading appearance of cold sores.
4. The viruses multiply in the nucleus of the host cells.
Papovaviridae
1. These are small viruses containing double-stranded DNA with 72 capsomeres.
2. They are nonenveloped viruses.
3. They replicate in the nucleus of host cell along with host cell chromosome.
4. This may cause host cells to proliferate, resulting in a tumor.
Hepadnaviridae
