Hypothesis of Origin
Endogenous retroviruses are a variant of a retrovirus which became permanently integrated with its host and is inherited from generation to generation as part of the genome of the host.
Retroviruses are single-stranded RNA viruses that reverse-transcribe their RNA into DNA for integration into the host's genome. Most retroviruses (such as HIV-1) infect somatic cells, but in very rare cases, it is thought that exogenous retroviruses have infected germline cells (cells that make eggs and sperm) allowing integrated retroviral genetic sequences to be passed on to subsequent progeny, thereby becoming 'endogenous'. Endogenous retroviruses have persisted in the genome of their hosts for thousands of years. However, they are generally only infectious for a short time after integration as they acquire many inactivating mutations during host DNA replication. They can also be partially excised from the genome by a process known as recombinational deletion. They are thought to play a key role in evolution. Some human ERVs have been implicated in ALS, certain autoimmune diseases, and cancers.
Read more about this topic: Endogenous Retrovirus
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