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Why do chloroplasts and mitochondria have their own DNA?

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“mermaid's wine glass” algae — Algae The macroscopic genus of algae known as *Acetabularia* is commonly called “mermaid's wine glass” because of the distinctive umbrella-like shape of the tips of its stalks.

Chloroplasts and mitochondria possess their own DNA because they are believed to be the descendants of free-living prokaryotic organisms that were incorporated into ancestral eukaryotic cells through a process known as endosymbiosis.312

According to the endosymbiont hypothesis, these organelles originated as independent bacteria—specifically cyanobacteria in the case of chloroplasts—that formed stable, symbiotic associations with host cells. Over evolutionary time, these internalized organisms integrated into the host cells, losing their ability to survive independently while retaining their distinct, circular DNA and protein-synthesizing machinery.34526

This extranuclear DNA, which lacks the histones associated with eukaryotic nuclear DNA, serves as evidence of their prokaryotic ancestry. Because they replicate independently of the cell's nucleus and contain genetic instructions for their own activities—such as photosynthesis in chloroplasts and energy production in mitochondria—they remain distinct from other cellular organelles.16425