It is now generally accepted that mitochondria and chloroplasts originated as fr

Question

It is now generally accepted that mitochondria and chloroplasts originated as free-living bacteria that were engulfed by an ancestral eucaryotic cell. However, it is also known that the mitochondrial DNA and the chloroplast DNA lack genes for many essential functions. This means that, were the mitochondria or the chloroplast to “escape” the modern day eucaryotic cell, the mitochondria or the chloroplasts could not survive on their own. Explain what has happened that allows the mitochondria and chloroplasts to survive in the host cell, even though they lack the DNA encoding essential genes in their DNA.

Explanation / Answer

One hypothesis was that initially chloroplasts/mitochondria were independent free living organisms. They contained all the essential genes required for their survival. Once they got ingested and lost autonomy, some its essential genes were lost during the course of evolution.

In the absence of essential genes, they could maintain themselves due to the support of the nuclear genome. Many of these organellar proteins are encoded by the nuclear geneome and transported into them.

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