5 ms·

Do you know an article about that? Did not find anything about a life form without DNA, except http://news.nationalgeographic.com/news/2010/12/101202-nasa-annou

by davnn 10y ago

Do you know an article about that? Did not find anything about a life form without DNA, except http://news.nationalgeographic.com/news/2010/12/101202-nasa-announcement-arsenic-life-mono-lake-science-space/ http://news.nationalgeographic.com/news/2010/12/101202-nasa-.... The definition of life itself is not really obvious to me either, some sources count viruses as life other don't.

Lyaserkiev 10y ago
I'm guessing he means RNA viruses https://en.m.wikipedia.org/wiki/RNA_virus https://en.m.wikipedia.org/wiki/RNA_virus
Retric 10y ago
The definition of life is a tricky question. The most obvious example is red blood cells dump their DNA. So they can't replicate, and virus can't target them. However, insect drones also can't reproduce and are considered alive so it's a little more open to debate than you might think. As to life without DNA. The methodology is somewhat in question for this but here is a more in depth link: http://science.sciencemag.org/content/332/6034/1163.full http://science.sciencemag.org/content/332/6034/1163.full Now, this is really 1:1 with DNA just using slightly different chemistry, but it's hard to call something DNA when you swap out one of the building blocks. Other examples are hard to locate in large part because you can't direct detect this stuff. Anyway, my point was while a virus is 'stuck' using DNA as it needs to infect things that use DNA. However, they can use RNA internally. PS: For a really out there example, prions seem really close to life.
- kens 10y ago
  The paper you cite about the bacterium that uses arsenic instead of phosphorus in its DNA was conclusively discredited. http://www.nature.com/news/arsenic-life-bacterium-prefers-phosphorus-after-all-1.11520 http://www.nature.com/news/arsenic-life-bacterium-prefers-ph...
  - Retric 10y ago
    This does not mean that arsenate does not get into the bacteria, he points out. “It just shows that this bacterium has evolved to extract phosphate under almost all circumstances.” Yes, it really wants phosphorus. But, a strong preference does not create phosphorus when there is none to be found. Not that single cells really want or try etc, but you get the idea.
- derekp7 10y ago
  One definition that I like to include in defining life, is something that uses energy to decrease (or maintain?) local entropy.

by davnn 10y ago

Lyaserkiev 10y ago

I'm guessing he means RNA viruses https://en.m.wikipedia.org/wiki/RNA_virus https://en.m.wikipedia.org/wiki/RNA_virus

Retric 10y ago

The definition of life is a tricky question. The most obvious example is red blood cells dump their DNA. So they can't replicate, and virus can't target them. However, insect drones also can't reproduce and are considered alive so it's a little more open to debate than you might think. As to life without DNA. The methodology is somewhat in question for this but here is a more in depth link: http://science.sciencemag.org/content/332/6034/1163.full http://science.sciencemag.org/content/332/6034/1163.full Now, this is really 1:1 with DNA just using slightly different chemistry, but it's hard to call something DNA when you swap out one of the building blocks. Other examples are hard to locate in large part because you can't direct detect this stuff. Anyway, my point was while a virus is 'stuck' using DNA as it needs to infect things that use DNA. However, they can use RNA internally. PS: For a really out there example, prions seem really close to life.

kens 10y ago
The paper you cite about the bacterium that uses arsenic instead of phosphorus in its DNA was conclusively discredited. http://www.nature.com/news/arsenic-life-bacterium-prefers-phosphorus-after-all-1.11520 http://www.nature.com/news/arsenic-life-bacterium-prefers-ph...
- Retric 10y ago
  This does not mean that arsenate does not get into the bacteria, he points out. “It just shows that this bacterium has evolved to extract phosphate under almost all circumstances.” Yes, it really wants phosphorus. But, a strong preference does not create phosphorus when there is none to be found. Not that single cells really want or try etc, but you get the idea.
derekp7 10y ago
One definition that I like to include in defining life, is something that uses energy to decrease (or maintain?) local entropy.