Viral Replication – Student Notes
🧬 Viral Replication – Student Notes
1. Basic Concept of Viral Replication
Viruses must infect a host cell to replicate.
They have host specificity (Tropism) → specific cells & organisms.
Virus needs to:
1- Alter host cell machinery
2- Replicate its genome
3- Package genome into new virions
2. Site of Replication (Very Important)
📍 In Nucleus:
Most DNA viruses (except poxvirus)
Orthomyxovirus (Influenza)
Retroviruses
📍 In Cytoplasm:
Most RNA viruses
Poxvirus (exception: DNA virus but cytoplasmic)
3. Special Viral Properties (High-Yield)
Reverse Transcriptase:
Retroviruses
Hepatitis B virus
RNA-dependent RNA polymerase:
, (-) RNA viruses
dsRNA viruses
Segmented genome (Reassortment):
Influenza
Reoviruses
Syncytia formation (fusion cells):
RSV, Measles, HIV
Cancer-associated viruses:
HPV, EBV, HBV, HCV
4. Unique Viruses
🧪 Poxvirus
Replicates in cytoplasm
Encodes its own DNA-dependent RNA polymerase
🧪 Hepadnavirus (HBV)
Partially dsDNA
Has:
Reverse transcriptase
RNase activity
DNA polymerase ➡️ Multifunctional enzyme
5. General Steps of Viral Replication
1️⃣ Adsorption (Attachment)
Virus binds receptor
Requires Ca²⁺ or Mg²⁺
2️⃣ Entry
🧬 Viral Replication – Student Notes
1. Basic Concept of Viral Replication
Viruses must infect a host cell to replicate.
They have host specificity (Tropism) → specific cells & organisms.
Virus needs to:
1- Alter host cell machinery
2- Replicate its genome
3- Package genome into new virions
2. Site of Replication (Very Important)
📍 In Nucleus:
Most DNA viruses (except poxvirus)
Orthomyxovirus (Influenza)
Retroviruses
📍 In Cytoplasm:
Most RNA viruses
Poxvirus (exception: DNA virus but cytoplasmic)
3. Special Viral Properties (High-Yield)
Reverse Transcriptase:
Retroviruses
Hepatitis B virus
RNA-dependent RNA polymerase:
, (-) RNA viruses
dsRNA viruses
Segmented genome (Reassortment):
Influenza
Reoviruses
Syncytia formation (fusion cells):
RSV, Measles, HIV
Cancer-associated viruses:
HPV, EBV, HBV, HCV
4. Unique Viruses
🧪 Poxvirus
Replicates in cytoplasm
Encodes its own DNA-dependent RNA polymerase
🧪 Hepadnavirus (HBV)
Partially dsDNA
Has:
Reverse transcriptase
RNase activity
DNA polymerase ➡️ Multifunctional enzyme
5. General Steps of Viral Replication
1️⃣ Adsorption (Attachment)
Virus binds receptor
Requires Ca²⁺ or Mg²⁺
2️⃣ Entry
