Question

we've learned that mitochondria and chloroplasts have their own DNA, BUT ONLY A SMALL FRACTION compared to the prokaryotes that biologists have identified as their closest, free-living ancestors. Most of the mitochondrion genome has been transferred to the host nucleus. Why do you think the mitochondria still has the remnants of a few genes and didn't transfer all its genome to the host nucleus?

Answer 1

Answer:

In humans Mitochondria has got about 37 genes in its circular DNA. It is contributed from maternal cell or ovum.

The presence of mitochondrial gene remnants can be proved by its expression.

Of the 37 genes 13 give instruction for production of enzymes, for oxidative phosphorylation. The remaining genes give instruction for formation of rRNA and tRNA.

Once we expell the circular gene from mitochondria, the cell stops oxidative phosphorylation and eventually it dies.

Considering other eukaryotes, mitochondria is diverse in its genome and even action or role.

Mitochondria of some worms as fasciola hepatic, are anaerobic mitochondria. They don't use oxygen as terminal acceptor and produce only 5 moles of ATP from 1mole glucose as compared to 36 in aerobic mitochondria.

Yet another group of mitochondria produce ATP from fermentation. Molecular hydrogen will be end product. They are seen in trichomonads.

4th category is inconspicuous mitochondria. That is not at all involved in ATP production.

The main differences in these mitochondria are in their holding genes.