Baltimore Classification System. →This System is developed by david baltimore". →The baltimore classification system is a scheme for classifying viruses based on the type of genome and it's replication. (07) →David baltimore a nobel laureate, to propose a : and inspired him classification, popularly known as baltimore scheme, based on the fundamental importance of mRNA in the replication cycle of virus. → Baltimore classification divided all viruses, irrespective of their host, into 7 classes and each is commonly referred to by the nature of the virus genome in that class I: Double Stranded DNA viruses. I: Single Stranded DNA viruses. Ⅲ: Double Stranded RNA, Viruses TV: Positive Single Stranded RNA viruses. : Negative single Stranded RNA viruses. : Single stranded RNA genome that replicate with DNA intermediate. : Double Stranded DNA genome that replicates with RNA intermediate. clas Class-I: Double Stranded DNA Viruses:- Double Stranded DNA virus enters the host nucleus before it begins to replicate. → It makes use of the host polymerases to replicate it's genome, and is therefore highly dependent on the host cell cycle.. The cell must there fore be in replication for the virus to replicate. Examples: Herpes viridae papo viridae. , Adeno viridae and. class- :- single Stranded DNA viruses:- Most of the single stranded ONA virus have circular genomes and replicate mostly with in the nudeus by a rolling circle mechanism. Examples: Anello viridae Parvo viridae. circo viridae and Class Double Stränded RNA - Viruses:- Double Stranded RNA Viruses replicate in in the host cell cytoplasm... the "core capsid And they do depend, as, heavily on host polymerase, as DNA viruses. →The genome class-III viruses may Each gene codes for only one protein. be segmented. Examples: Rheo viridae and Birna viridae. class-iv single Stranded RNA genome with tve Sense:- Sense Single Stranded RNA virus can be directly →The tve Sense accessed by, host ribosome to translate into proteins. →The replication and reproduction occur in cytoplasm →It contains polajeistronic mRNA....... This polycistronic mRNA is translated into a poly- protein that is subsequently cleaved to form separate proteins Examples: corona viridae T Flavi viridae and picorna viridae. Astro viridae class-v- Single Stranded Sense- RNA genome with -ve → The -ve Sense can not" directly Single Stranded RNA viruses are accessed by the host ribosome to translate înto proteins. → This genome may be segmented or non-Segmented. Examples: ortho myro viridae Rhabo viridae. Para myxo viridae and class-v1: Single stranded RNA genome that replicate : with DNA Intermediate:- → Single Stranded RNA genome that replicate with DNA intermediate. The RNA is converted to DNA by reverse transcriptase. →Instead of using RNA for template protein they use DNA as a templates........ →And then DNA is Spliced into the host genome for Subsequent transcription and translation by using enzyme integrase. Examples! It includes retroviruses such as HIV and as well as Meta viridae and pseudoviridae. -class:- Double Stranded ONA genome that replicates with RNA intermediate:- These are → the small group of viruses. →They replicate via single stranded RNA intermediate. →The double stranded genome DNA is gapped, and Subsequently filled in to form of closed circle Serving MRNA. as a template for production of viral →To reproduce genome, RNA is reverse transcribed back to DNA. → Hepatitis B is a class-vil virus.