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Home Q & A Board Biology-Related Homework Help Zoology and Botany (Moderator: ehd123)
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julia.k18 julia.k18
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11 years ago
How do most biologist think that the mitochondria and chloroplasts of eukaryotic cells originate? What is the evidence for this idea?
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#1
11 years ago
They were symbiotic bacteria that lived within a host cell and eventually became part of it.

Both organelles have their own genomes, prokaryotic genomes that make prokaryotic mRNA which is translated into prokaryotic proteins.

Very odd system to be within a eukaryote.

Sequencing those genomes revealed them to be very similar to alpha proteobacteria and cyanobacteria, respectively.

There are also amoebas that have a symbiotic relationship with cyanobacteria, which function as chloroplasts.
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#2
11 years ago
There are additional things that support this whole endosymbiotic idea. Both chloroplasts and mitochondria have ribosomes, and those ribosomes have the same structure as bacterial ribosomes, and are much smaller and simpler than the ribosomes in the cytoplasm. Both of those organelles have their own chromosome,  and it is a circular DNA molecule, just as bacterial chromosomes are.
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#3
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11 years ago
In addition, these organelles have double membrane, which is a sign that they might be the result of phagocytosis.
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#4
11 years ago
They both have their own unique DNA, and they are small enough to be considered bacteria.
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