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Larry Moran has an interesting series on his Sandwalk blog about what, exactly constitutes "functional" DNA. The first part, found here:
http://sandwalk.blogspot.ca/2014/06/...rs-part-i.html
is more of a detailed discussion of what function is and what it's not. The second part, closely related, is here:
http://sandwalk.blogspot.com/2014/07...t-ii.html#more
focuses on "junk DNA" and the difficulty of defining it. Moran himself confuses the matter by defining "functional" and "junk" DNA as being both exclusive and exhaustive -- that is, all DNA that is nonfunctional is junk. Which of course begs the question of what "functional" means.
These are long entries with lots of comments, and they do go into such matters as degree to which sequences are conserved, and whether "spacer" sequences whose length and location but not whose ordering is conserved, should be considered functional.
He also discusses the distinction between historical and empirical approaches to function.
The details in dispute over exactly what qualifies as a function, according to which definitions and measurements, populations and time scales, is pretty interesting. The bottom line seems to be that most eukaryotic genomes contain a great deal of DNA that serves no function no matter how inclusive the definition, and that most genomes are pretty well mapped by now.
http://sandwalk.blogspot.ca/2014/06/...rs-part-i.html
is more of a detailed discussion of what function is and what it's not. The second part, closely related, is here:
http://sandwalk.blogspot.com/2014/07...t-ii.html#more
focuses on "junk DNA" and the difficulty of defining it. Moran himself confuses the matter by defining "functional" and "junk" DNA as being both exclusive and exhaustive -- that is, all DNA that is nonfunctional is junk. Which of course begs the question of what "functional" means.
These are long entries with lots of comments, and they do go into such matters as degree to which sequences are conserved, and whether "spacer" sequences whose length and location but not whose ordering is conserved, should be considered functional.
He also discusses the distinction between historical and empirical approaches to function.
The details in dispute over exactly what qualifies as a function, according to which definitions and measurements, populations and time scales, is pretty interesting. The bottom line seems to be that most eukaryotic genomes contain a great deal of DNA that serves no function no matter how inclusive the definition, and that most genomes are pretty well mapped by now.