Viral genetics is the study of the mechanisms of heritable information in viruses, including their genome structure, replication, genetic change, and analysis. Viruses are genetic parasites that cannot multiply until reaching a host cell, where they must carry genes to synthesize their capsid and regulate host actions. Most viruses have RNA genomes, though some have DNA, and their replication occurs in the host cell cytoplasm or nucleus depending on genome type. Viruses undergo genetic changes through mutation and recombination during replication in host cells.

2. Viral Genetics
Saad Anwar
Microbiologist
Allama Iqbal open university
Islamabad Pakistan
Topic

3. Introduction
 Viral genetics is the study of the mechanisms of heritable information in viruses,
including genome structure, replication, genetic change and genome analysis of
viruses.
 Disease causing viruses are of particular interest, however geneticists also use
viruses to help understand fundamental mechanisms of molecular genetics.

4. Nature of Viruses
 Viruses are considered as genetic parasites, because they cannot multiply until
their nucleic acid has reached the internal habitat of the host cell.
 At minimum, must carry genes for synthesizing viral capsid, and genetic material
for regulating actions of host, and for packaging mature viruses.

5. DNA and RNA Viruses
 A virus has either a DNA or an RNA genome and is called a DNA virus or an RNA virus,
respectively.
 The vast majority of viruses have RNA genomes.
 Plant viruses tend to have single-stranded RNA genomes and bacteriophages tend to have
double-stranded DNA genomes.
 The genome replication of most DNA viruses takes place in the cell's nucleus.
 Replication usually takes place in the cytoplasm.

6. Cont.…….
 Classification
 Baltimore classification
 ICTV classification

7. Genetic Change in Viruses
 Viruses are continuously changing as a result of genetic selection.
 They undergo subtle genetic changes through mutation.
 And major genetic changes through recombination.

8. Viral Replication
 Viral replication is the formation of biological viruses during the infection process in the target host
cells.
 Viruses must first get into the cell before viral replication can occur.
Steps
 Adsorption
 Penetration
 Uncoating
 Viral genome replication
 Maturation
 Release

9. Genome Analysis
 Viral genomes are the fastest evolving entities in biology, mainly because of their short replication
time and the large quantity of offspring released per cell infected.
 Evolution occurs by several mechanisms: Random mutation, recombination, reassortment, gene
amplification/reduction; and results in quasispecies and defective interfering genomes.