= Retroviridae
{c}
<Retroviridae> is a <taxonomic family> of enveloped <viruses> whose replication involves <reverse transcription> and integration of the resulting DNA into host-cell DNA. The integrated form is a <provirus>, from which host machinery can make viral RNA. Thus the replication cycle links RNA and DNA forms rather than remaining entirely in one nucleic-acid form.<Retroviridae report by the International Committee on Taxonomy of Viruses>[Summary and Table 1, replication]{ref}
A <virion> contains a <viral envelope>, an internal core, genomic nucleic acid and replication enzymes. <Orthoretrovirinae> package a dimer of single-stranded RNA. In <Spumaretrovirinae>, reverse transcription can already be partly completed in the particle, so a family-wide description should not require every virion to contain only RNA.<Retroviridae report by the International Committee on Taxonomy of Viruses>[Table 1, virion and genome]{ref}
<HIV-1>, in the genus <Lentivirus>, is one member of this broader family. The family name therefore supplies a classification shared by multiple genera, rather than another name for HIV-1 alone.
The RNA-to-DNA-to-RNA cycle also clarifies measurement. A test detecting a proviral DNA sequence addresses a different molecular form from a test detecting packaged RNA. Demonstrating one intermediate can support the proposed replication pathway, but its abundance alone does not count every completed infectious particle. The assay must identify which stage and material it measures.
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