/usr/share/gromacs/top/amber96.ff/dna.arn is in gromacs-data 4.5.5-2.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 | DNA OP1 O1P
DNA OP2 O2P
DNA H2' H2'1
DNA H2'' H2'2
DNA H5' H5'1
DNA H5'' H5'2
DNA HO5' H5T
DNA HO3' H3T
|