<P> The popular term "powerhouse of the cell" was coined by Philip Siekevitz in 1957 . </P> <P> In 1967, it was discovered that mitochondria contained ribosomes . In 1968, methods were developed for mapping the mitochondrial genes, with the genetic and physical map of yeast mitochondrial DNA being completed in 1976 . </P> <P> There are two hypotheses about the origin of mitochondria: endosymbiotic and autogenous . The endosymbiotic hypothesis suggests that mitochondria were originally prokaryotic cells, capable of implementing oxidative mechanisms that were not possible for eukaryotic cells; they became endosymbionts living inside the eukaryote . In the autogenous hypothesis, mitochondria were born by splitting off a portion of DNA from the nucleus of the eukaryotic cell at the time of divergence with the prokaryotes; this DNA portion would have been enclosed by membranes, which could not be crossed by proteins . Since mitochondria have many features in common with bacteria, the endosymbiotic hypothesis is more widely accepted . </P> <P> A mitochondrion contains DNA, which is organized as several copies of a single, usually circular, chromosome . This mitochondrial chromosome contains genes for redox proteins, such as those of the respiratory chain . The CoRR hypothesis proposes that this co-location is required for redox regulation . The mitochondrial genome codes for some RNAs of ribosomes, and the 22 tRNAs necessary for the translation of messenger RNAs into protein . The circular structure is also found in prokaryotes . The proto - mitochondrion was probably closely related to the Rickettsia . However, the exact relationship of the ancestor of mitochondria to the alphaproteobacteria and whether the mitochondrion was formed at the same time or after the nucleus, remains controversial . </P>

Mitochondria is the powerhouse of a cell﻿