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Agood10 t1_irkikwk wrote

If you consider viruses “alive” then it’ll probably be a virus.

Circoviruses have a genome size of 0.89kbases (890 bases)

If you don’t count viruses, the bacteria mycoplasma genitalium has a genome size of ~580kbases (580,000)

For comparison, humans have a genome size of ~6.4Gbases (6,400,000,000) or 3.2Gbases if you want the haploid number (per another users comment)

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CinnabarErupted t1_irkna4h wrote

If you consider viruses alive, then the answer is a transposon. It's just the bare minimum genetic sequence needed to reproduce parasitically. Sorry OP, the answer depends on your definition of life - I hope you enjoy discovering where your definitional lines are drawn!

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LoverOfPie t1_irl9ho6 wrote

How short are those?

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CinnabarErupted t1_irla561 wrote

They get down to about 100bp. All they need is the gene encoding the enzyme needed to insert or cut them from the host genome (a transposase), genetic control elements to ensure it gets expressed in the host (can be just a tiny promoter), and the recognition sequence for the transposase at either end of its genome. It's basically the precursor to viruses - parasitic replication, but without any structural elements needed.

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viridiformica t1_irmgugo wrote

What about prions? Reproduction of a sort with no genetic material necessary

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Taalnazi t1_irmd9jy wrote

And viroids? Which place do they take?

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-Metacelsus- t1_irkjncz wrote

> humans have a genome size of ~6.4Gbases (6,400,000,000)

Note, this is the diploid genome size which is 2 copies of the haploid genome.

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perta1234 t1_irlzhxd wrote

Genome is one full set of chromosomes, so haploid is the correct number. This was the first time I saw anyone suggesting the diploid amount of DNA as genome size. Wonder how one would handle the mitochondrial genome using that approach? The number of them varies greatly, though I guess their share is about 1% only.

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Rynox2000 t1_irkyks9 wrote

If this isn't a sign of the universe providing competition at every level, nothing is.

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bingybunny t1_irlhr0p wrote

I read Planet of Viruses last year. it was fascinating. humans have dna from viruses, there's a vast soup of viruses, phages and other little snippets of DNA that we swim in, there's like a continuum of interactions of life at all levels of size and complexity

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coolidfors t1_irn7oim wrote

Is it wrong to consider virus something between living and non-living? Something like a stepping stone?

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Agood10 t1_irn8ytp wrote

I think it’s all a matter of opinion, where to draw the line on what is and isn’t considered life. But yes, I can see how one could consider them somewhere between alive and not. They meet many of the criteria we’ve somewhat arbitrarily defined for living things but miss others, such as having the ability to produce their own energy for survival and replication.

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