What do you understand about Endosymbiosis? Ok, let me do a summary after have being study about this topic! How can this organism resemble the early step of evolution from a prokaryotic cell to the advance eukaryotic cell? It was began such as figure below.
The reason why in genetic study, researcher use the mitochondria rather than using nucleus as the mitochondrian actually poses it own genetic material which differ from genetic material contain in nuclear. This is because, mitochondria DNA (mtDNA) only could be passed down from mother but not for nucleus as it could be passed through physical factor.
Watch this video to understand more detail about endosymbiosis process :)