Eukaryote-cell organelles can come from eubacteria incorporated into cells {endosymbiosis theory}. Plant chloroplasts came from cyanobacteria. Animal mitochondria came from purple photosynthetic bacteria. For example, Cryptomonas phytoflagellate combines eukaryotic nucleus, photosynthetic prokaryote, and eukaryotic cell.
Evolution has added introns to, and subtracted introns from, DNA, possibly to aid exon recombination {exon shuffling} and combine protein functions.
Bacteria have one circular chromosome {monoploid}|. Polyploid protozoa have several linear-chromosome copies. Perhaps, bacteria are simplified polyploid protozoa.
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Date Modified: 2022.0225