3 ms·

Is pretty damn perfect for a chemical process. Each replication of the genome introduces only one error on average and given that the majority of the genome is

by mrestko 11y ago

Is pretty damn perfect for a chemical process. Each replication of the genome introduces only one error on average and given that the majority of the genome is junk DNA (not just non-coding, but actual junk), the single error is roughly analogous to a speck in the margin of a photocopied page.

outworlder 11y ago
Is it, though? I thought that the 'junk' DNA thing was a myth.
- hemicyclium 11y ago
  There has been renewed interest in finding out what non-coding DNA (aka 'junk' DNA) actually does. Some prominent theories are that some kinds of non-coding DNA are epigenetic controls, but there isn't a complete set of theories yet. There ARE transposable elements, sequences of DNA that can essentially move around in your genome at will, and cause problems by doing so: imagine getting a transport protein sequence in a stem cell cut in half. Even then, these are kind of like DNA parasites, not junk.
  - coriny 11y ago
    Sorry, I'm going to nit pick, but non-coding and "junk" aren't the same thing: Non-coding just refers to not being translated to protein, and we know (as you list, more for the benefit of others) that there are many non-coding functional elements. Junk DNA is non-conserved DNA (e.g. shows only neutral selection). And if it's not being selected for or against, then it probably doesn't have much effect either way.
- coriny 11y ago
  I think people get emotive over the term 'junk'. It was always just a phrase rather than a technical description. We know that ~80%, maybe a little more, of the genome does not show conservation. If the function was important to the survival of the organism it have been selected for and thus evolutionarily conserved - hence the 85% "junk" figure. This does not mean that it isn't entirely biochemically inactive, or that there are some longer range periodicities in the sequence that are not elucidated. And as another commenter has noted, about half of the genome is composed of remnants of the Alu element, which jump about occasionally, but mostly degrade into total inactivity (sometimes being reactivated by recombining broken parts together). What has gained a lot of attention was the massive ENCODE project, which sought to provide a detailed atlas of biochemical function in the human genome. The headline figure from there has been that 80% of the human genome has some function. There's a lot of controversy (understatement hat on) on the basic experimentation done for ENCODE, the structure of the project, the usefulness of the data produced and how they define biological activity. The debate possibly got a bit out of control - the most sarcastic peer reviewed article I have ever read stirred the pot a bit (for more info: http://www.scilogs.com/next_regeneration/the-encode-controversy-and-professionalism-in-science/ http://www.scilogs.com/next_regeneration/the-encode-controve...). I think most biologists (warning, personal opinion) would still hold that 80% of the genome is not meaningfully biologically functional.

by mrestko 11y ago

outworlder 11y ago

Is it, though? I thought that the 'junk' DNA thing was a myth.

hemicyclium 11y ago
There has been renewed interest in finding out what non-coding DNA (aka 'junk' DNA) actually does. Some prominent theories are that some kinds of non-coding DNA are epigenetic controls, but there isn't a complete set of theories yet. There ARE transposable elements, sequences of DNA that can essentially move around in your genome at will, and cause problems by doing so: imagine getting a transport protein sequence in a stem cell cut in half. Even then, these are kind of like DNA parasites, not junk.
- coriny 11y ago
  Sorry, I'm going to nit pick, but non-coding and "junk" aren't the same thing: Non-coding just refers to not being translated to protein, and we know (as you list, more for the benefit of others) that there are many non-coding functional elements. Junk DNA is non-conserved DNA (e.g. shows only neutral selection). And if it's not being selected for or against, then it probably doesn't have much effect either way.
coriny 11y ago
I think people get emotive over the term 'junk'. It was always just a phrase rather than a technical description. We know that ~80%, maybe a little more, of the genome does not show conservation. If the function was important to the survival of the organism it have been selected for and thus evolutionarily conserved - hence the 85% "junk" figure. This does not mean that it isn't entirely biochemically inactive, or that there are some longer range periodicities in the sequence that are not elucidated. And as another commenter has noted, about half of the genome is composed of remnants of the Alu element, which jump about occasionally, but mostly degrade into total inactivity (sometimes being reactivated by recombining broken parts together). What has gained a lot of attention was the massive ENCODE project, which sought to provide a detailed atlas of biochemical function in the human genome. The headline figure from there has been that 80% of the human genome has some function. There's a lot of controversy (understatement hat on) on the basic experimentation done for ENCODE, the structure of the project, the usefulness of the data produced and how they define biological activity. The debate possibly got a bit out of control - the most sarcastic peer reviewed article I have ever read stirred the pot a bit (for more info: http://www.scilogs.com/next_regeneration/the-encode-controversy-and-professionalism-in-science/ http://www.scilogs.com/next_regeneration/the-encode-controve...). I think most biologists (warning, personal opinion) would still hold that 80% of the genome is not meaningfully biologically functional.