Endosymbiont terminology has been shifted over to different departments, so to cover up the gain of function processes.

Endosymbiont
Gain of Function

Retron Non-Coding RNA (ncRNA)

Reverse-Transcribed DNA (RT-DNA)

Recombinant DNA (rDNA)

Mitochondrial DNA (mtDNA)

https://en.m.wikipedia.org/wiki/Retron

https://en.m.wikipedia.org/wiki/Recombinant_DNA

https://en.m.wikipedia.org/wiki/Mitochondrial_DNA

https://en.m.wikipedia.org/wiki/Non-coding_RNA

https://en.m.wikipedia.org/wiki/Reverse_transcriptase

https://en.m.wikipedia.org/wiki/MicroRNA

https://en.m.wikipedia.org/wiki/Chimera_(genetics)

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Retron is a distinct DNA sequence found in the genome of many bacteria species that codes for reverse transcriptase and a unique single-stranded DNA/RNA hybrid called multicopy single-stranded DNA (msDNA).

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Horizontal transmission and recombination maintain forever young bacterial symbiont genomes

https://www.ncbi.nlm.nih.gov/labs/pmc/articles/PMC7473567/

Intrahost Genetic Diversity of Bacterial Symbionts Exhibits Evidence of Mixed Infections and Recombinant Haplotypes

https://academic.oup.com/mbe/article/34/11/2747/3925276

Rare creation of recombinant mtDNA haplotypes in mammalian tissues

https://www.pnas.org/content/102/17/6057

Precise genome editing across kingdoms of life using retron-derived DNA

https://www.nature.com/articles/s41589-021-00927-y

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https://en.m.wikipedia.org/wiki/Fibroblast_growth_factor

https://en.m.wikipedia.org/wiki/Interferon_gamma

https://en.m.wikipedia.org/wiki/Macrophage

https://en.m.wikipedia.org/wiki/Chronic_granulomatous_disease

https://en.m.wikipedia.org/wiki/Herpesviridae