NEET BIOLOGY

Detailed explanation-1: -There are two kinds of endogenous viruses: endogenous retroviruses, and rare RNA virus integration.

Detailed explanation-2: -Integration is an obligatory replication step for all retroviruses. The process begins after the virus enters the cell and the RNA genome is reverse transcribed into a double-stranded DNA. The direct precursor to integration is the linear form of viral DNA (4, 64).

Detailed explanation-3: -There are two processes used by viruses to replicate: the lytic cycle and lysogenic cycle. Some viruses reproduce using both methods, while others only use the lytic cycle.

Detailed explanation-4: -Viruses are much smaller than bacteria and consist of a single-or double-stranded nucleic acid (DNA or RNA) surrounded by a protein shell called a capsid; some viruses also have an outer envelope composed of lipids and proteins. They vary in shape. The two main classes are RNA viruses and DNA viruses.

Detailed explanation-5: -Viral genome integration into the host genome is a hallmark of retroviruses, as it is a mandatory step in the retroviral life cycle and a prerequisite for productive infection.