Wittkowski transmission disequilibrium test
This annotation indicates the presence of a genetic linkage between a genetic marker and a genetic trait.
The calculation is based on the derivation described in http://en.wikipedia.org/wiki/Transmission_disequilibrium_test#A_modified_version_of_the_TDT.
Note that this annotation requires a valid ped file.
GATK version 3.3-0-g37228af built at 2014/10/24 14:40:51. GTD: NA