virology: replicative cycle

virus replication steps

1. attachment
2. penetration
3. uncoating
4. synthesis
5. assembly
6. release

attachment

the actual binding of spike proteins on the virus to the host cell receptors.

true or false: unlike bacteria, which can generally infect tissues, viruses have specific cells that they invade

true

penetration

also known as viral entry and can occur by breaking through the membrane, endocytosis, or membrane fusion

endocytosis

may or may not be receptor-mediated

membrane fusion

results in viral proteins being incorporated into the host membrane

uncoating

which can sometimes occur simultaneously with penetration, involves the capsid breaking open and the viral genomic material being released

synthesis

sometimes known as biosynthesis or viral replication, is the actual creation of viral genomic material and viral proteins. essentially starts with one original copy and makes more

DNA-dependent RNA Polymerase (DdRP)

DNA viruses: DNA to RNA

RNA-dependent RNA Polymerase (RdRP)

RNA viruses. RNA to RNA. higher mutation rate

Reverse Transcriptase (RT)

Retro viruses. RNA back to DNA

early synthesis

involves expression of non-structural genes involved in genome replication it makes the machinery needed to replicate the genome

late synthesis

involves copying the genome and the synthesis of structural proteins

assembly

also known as maturation, consists of the viral genomic material and viral proteins being put together to make a new virus; this step can involve the assembly of hundreds or thousands of new virus particles

release

opposite of entry. can occur via budding

viral proteins

serve as an indicator of where to exit for enveloped viruses, which acquire the host membrane to become the viral envelope

lytic cycle

is the active release of new virus, often times resulting in alteration of cellular function or destruction of the cell itself

cytopathetic effects (CPE)

cause of sign and symptoms

budding

can go undetected without alerting the immune system

cellular lysis

kills cells, but alerts the immune system to fight off that virus

lysogenic cycle

cutting the genes, when the virus does not make new virus, but rather inserts its genomic material into the host chromosome, forming a provirus thereby resulting in replication of the viral