The intracellular parasite Nanoarchaeum equitans has one of the smallest prokaryotic genomes. Why is the genome of N. equitans so small?
How is it possible that the genome of N. equitans contains more genes than that of Mycoplasma genitalium, which is actually 90 kbp larger?
What will be an ideal response?
Answer: The intracellular parasite, N. equitans is a highly specialized archaeon with a very condensed genome, containing little noncoding DNA and no introns. It is well-adapted to live within its archaeon host and can hijack its host's proteins. It therefore does not require its own genes for energy consumption. N. equitans contains more genes that M. genitalium because there is very little noncoding DNA and can thus fit more ORFs into a smaller genome. This is very efficient, although it does not allow for changes in gene expression in response to environmental changes.
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