Genetic evidence (base sequences in their mitochondrial deoxyribonucleic acid [mtDNA] and ribosomal ribonucleic acid [rRNA]) now indicates that the following are more natural (evolutionarily related) groups of Protista.ome lack mitochondria and suggest what the first eukaryotes may have been like, while others have primitive mitochondria that closely resemble bacteria. Some basal Protista without mitochondria are Trichomonas, a vaginal parasite of humans; Giardia, an intestinal parasite; and Entamoeba, the cause of amoebic dysentery.