These "DNA" files are self contained html/css files related to a 2014 series in the FICTION section:
https://brooklynrail.org/2014/04/fiction/from-dna-apr2014
which redirects visitors to the html pages stored here
https://brooklynrail.org/fiction/DNA/dna_excerpt.html
$route['2014/02/fiction/(dna)'] = "public_controller/articleURLRedirect/$1";
$route['2014/03/fiction/(from-dna-mar14)'] = "public_controller/articleURLRedirect/$1";
$route['2014/04/fiction/(from-dna-apr2014)'] = "public_controller/articleURLRedirect/$1";
$route['2014/05/fiction/(from-dna-may14)'] = "public_controller/articleURLRedirect/$1";
Docs on who created this: