5 ms·

If they matched, another possibility is that a stable life most easily forms a specific way, or this way only. Knowing for sure wouldn't be possible until more

by castis 6y ago

If they matched, another possibility is that a stable life most easily forms a specific way, or this way only. Knowing for sure wouldn't be possible until more samples are found in the universe.

willis936 6y ago
This is about as likely as guessing a 1024 bit encrypted key. “Match” means “match”. Not “similar structure and behavior”. If it is the same DNA then the only compelling explanation is that it is from the same origin.
- deleted 6y ago
  [deleted]
- lawlessone 6y ago
  If it's DNA at all then it would be from the same origin? How likely is it that alien life would also use DNA?
  - gmuslera 6y ago
    Even if it is DNA, if it encodes the same proteins in the same way than the life here would a be very improbable event. Think in an alien alphabet looking like ours, but also making the same sounds and some common words and meanings with the similar looking symbols.
  - willis936 6y ago
    “Origin” in this case would be something in the very physically close and near term. Something that excludes the possibility of serious evolutionary change. Even relatively static species undergo mutations in the long term. So if something is an exact match it is evident that they came from the same time and place (within some reasonable window). The origin would implicitly be Earth in the 1960s.
- castis 6y ago
  I meant match, similarly to saying curtains and carpets match.
  - willis936 6y ago
    “Matching DNA” has only one meaning that I am aware of and it is an exact 1:1 sequence. The goal is to identify a living organism from DNA that has fallen off it. https://en.wikipedia.org/wiki/DNA_profiling https://en.wikipedia.org/wiki/DNA_profiling
    - castis 6y ago
      my apologies on not using terminology that suits you
tomp 6y ago
Even if there's a "good reason" that life forms in a specific way (e.g. water + carbon based, RNA & DNA encoding information, etc.) there's very little reason that DNA should encode proteins in exactly the way ours does (on Earth-based life, AFAIK the code is nearly universal, indicating common origin).
sandworm101 6y ago
There is an old line of thought on this, that views DNA/RNA as crystals. Crystals branch out/reproduce in predictable or unpredictable ways depending on scale. At large scales a dry lakebed may seem a mass of randomly-aligned crystals but at the smallest scale each crystal is identical. They each formed from the same starting conditions from which random precursors settled into identical patterns. Such logic would suggest that DNA/RNA, if beginning in near-identical conditions, might also settle into nearly-identical patterns. At large scales the crystals would appear different and random but at the smallest scales life could well be similar or even identical... if one sees life as a form of crystal.
gus_massa 6y ago
Nobody is sure, some parts are so nice that perhaps are inevitable, some parts are too random. DNA and RNA: Perhaps they are inevitable, and any lifeforms have the same molecules and bases. Perhaps some lifeform can use only the methylated versions? Is ribose inevitable? Is 3 bases per codon inevitable? But I think there is a chance for inevitability. The list of amino acids is somewhat random. We use 20, Some bacteria use a 1 or 2 more. And we can transform in place the amino acid inside a protein into another amino acid. I expect a similar list of 20+-5 amino acids. A perfect coincidence would be too hard, but it is not even true for terrestrial life. The most interesting part is the Genetic Code https://en.wikipedia.org/wiki/Genetic_code https://en.wikipedia.org/wiki/Genetic_code that translate the 4^3=64 combinations of bases in the DNA to the 20 amino acids. As far as we know it is random. It has some internal structure, for example the code is mostly like 16 blocks to encode 15 amino acids and a stop signal, and a few tweaks here and there to break some block to encode the other 5 amino acids. But as far as we know there are no reasons to choose each block as us. Some bacteria use versions with small tweaks, with one or two changes, so we know it if possible to change it, but very difficult to make a total rewrite. If the life out there use the same Genetic Code (with a few tweaks) it is almost sure it is related to us.
- nicholasjon 6y ago
  Along those lines, I had a college professor who had just published a paper (now 25 years old?) talking about why "the 20 amino acids." He was equal parts bombastic and brilliant, and for some reason this paper of his stuck with me all these years. https://www.sciencedirect.com/science/article/abs/pii/S0022519384711982 https://www.sciencedirect.com/science/article/abs/pii/S00225... Now, I'm not an expert or even an advanced layperson in this area, so I won't attempt to speak to the validity of the idea. I merely found the argument interesting at the time.
  - gus_massa 6y ago
    Did anyone advanced in this research line? It looks like a nice mathematical idea, but it is forced too much to fit into the genetic code. First they propose a genetic code that is totally unrelated to the current one. It can be perfectly the table of a totally different lifeform. The transition they propose looks too difficult, almost impossible. Probably we had a transition from RNA to DNA a loooong time ago, but they have a 1 to 1 translation, and the intermediate steps look useful. But no one is sure anyway. They propose a change where almost all the table changes and almost all the internal structure of the table change. It is very strange that they have 20 amino acids and no stop code. A proposal with 19 amino acids and a stop code looks more sensible. We know that it is possible to add new amino acids to the table (with enough time). I think the main problem is that using 19 amino acids and a stop code breaks the magical part of predicting the number 20 with pencil and paper. To make the table work, you need the correct transfer-RNA. To get all the symmetries in their model you need to be really lucky. In the block model of 15+1 you any random selection of tRNA is fine if it ignore the last base. Another big problem is that they predict that half of the proteins would have been constructed backward. But as they say this make proteins not fold correctly. They try to avoid the problem using palindromic proteins, that is not supported by evidence.

by castis 6y ago

If they matched, another possibility is that a stable life most easily forms a specific way, or this way only. Knowing for sure wouldn't be possible until more samples are found in the universe.

willis936 6y ago

This is about as likely as guessing a 1024 bit encrypted key. “Match” means “match”. Not “similar structure and behavior”. If it is the same DNA then the only compelling explanation is that it is from the same origin.

deleted 6y ago
[deleted]
lawlessone 6y ago
If it's DNA at all then it would be from the same origin? How likely is it that alien life would also use DNA?
- gmuslera 6y ago
  Even if it is DNA, if it encodes the same proteins in the same way than the life here would a be very improbable event. Think in an alien alphabet looking like ours, but also making the same sounds and some common words and meanings with the similar looking symbols.
- willis936 6y ago
  “Origin” in this case would be something in the very physically close and near term. Something that excludes the possibility of serious evolutionary change. Even relatively static species undergo mutations in the long term. So if something is an exact match it is evident that they came from the same time and place (within some reasonable window). The origin would implicitly be Earth in the 1960s.
castis 6y ago
I meant match, similarly to saying curtains and carpets match.
- willis936 6y ago
  “Matching DNA” has only one meaning that I am aware of and it is an exact 1:1 sequence. The goal is to identify a living organism from DNA that has fallen off it. https://en.wikipedia.org/wiki/DNA_profiling https://en.wikipedia.org/wiki/DNA_profiling
  - castis 6y ago
    my apologies on not using terminology that suits you

tomp 6y ago

Even if there's a "good reason" that life forms in a specific way (e.g. water + carbon based, RNA & DNA encoding information, etc.) there's very little reason that DNA should encode proteins in exactly the way ours does (on Earth-based life, AFAIK the code is nearly universal, indicating common origin).

sandworm101 6y ago

There is an old line of thought on this, that views DNA/RNA as crystals. Crystals branch out/reproduce in predictable or unpredictable ways depending on scale. At large scales a dry lakebed may seem a mass of randomly-aligned crystals but at the smallest scale each crystal is identical. They each formed from the same starting conditions from which random precursors settled into identical patterns. Such logic would suggest that DNA/RNA, if beginning in near-identical conditions, might also settle into nearly-identical patterns. At large scales the crystals would appear different and random but at the smallest scales life could well be similar or even identical... if one sees life as a form of crystal.

gus_massa 6y ago

Nobody is sure, some parts are so nice that perhaps are inevitable, some parts are too random. DNA and RNA: Perhaps they are inevitable, and any lifeforms have the same molecules and bases. Perhaps some lifeform can use only the methylated versions? Is ribose inevitable? Is 3 bases per codon inevitable? But I think there is a chance for inevitability. The list of amino acids is somewhat random. We use 20, Some bacteria use a 1 or 2 more. And we can transform in place the amino acid inside a protein into another amino acid. I expect a similar list of 20+-5 amino acids. A perfect coincidence would be too hard, but it is not even true for terrestrial life. The most interesting part is the Genetic Code https://en.wikipedia.org/wiki/Genetic_code https://en.wikipedia.org/wiki/Genetic_code that translate the 4^3=64 combinations of bases in the DNA to the 20 amino acids. As far as we know it is random. It has some internal structure, for example the code is mostly like 16 blocks to encode 15 amino acids and a stop signal, and a few tweaks here and there to break some block to encode the other 5 amino acids. But as far as we know there are no reasons to choose each block as us. Some bacteria use versions with small tweaks, with one or two changes, so we know it if possible to change it, but very difficult to make a total rewrite. If the life out there use the same Genetic Code (with a few tweaks) it is almost sure it is related to us.

nicholasjon 6y ago
Along those lines, I had a college professor who had just published a paper (now 25 years old?) talking about why "the 20 amino acids." He was equal parts bombastic and brilliant, and for some reason this paper of his stuck with me all these years. https://www.sciencedirect.com/science/article/abs/pii/S0022519384711982 https://www.sciencedirect.com/science/article/abs/pii/S00225... Now, I'm not an expert or even an advanced layperson in this area, so I won't attempt to speak to the validity of the idea. I merely found the argument interesting at the time.
- gus_massa 6y ago
  Did anyone advanced in this research line? It looks like a nice mathematical idea, but it is forced too much to fit into the genetic code. First they propose a genetic code that is totally unrelated to the current one. It can be perfectly the table of a totally different lifeform. The transition they propose looks too difficult, almost impossible. Probably we had a transition from RNA to DNA a loooong time ago, but they have a 1 to 1 translation, and the intermediate steps look useful. But no one is sure anyway. They propose a change where almost all the table changes and almost all the internal structure of the table change. It is very strange that they have 20 amino acids and no stop code. A proposal with 19 amino acids and a stop code looks more sensible. We know that it is possible to add new amino acids to the table (with enough time). I think the main problem is that using 19 amino acids and a stop code breaks the magical part of predicting the number 20 with pencil and paper. To make the table work, you need the correct transfer-RNA. To get all the symmetries in their model you need to be really lucky. In the block model of 15+1 you any random selection of tRNA is fine if it ignore the last base. Another big problem is that they predict that half of the proteins would have been constructed backward. But as they say this make proteins not fold correctly. They try to avoid the problem using palindromic proteins, that is not supported by evidence.