Contains no header line, and one line per sample with 2V+6 fields where V is the number of variants.
The first six fields are the same as those in a .fam file. The seventh
and eighth fields are allele calls for the first variant in the .map
file ('0' = no call); the 9th and 10th are allele calls for the second
variant; and so on
That being said I thought PED files are formatted more regularly like so:
U_G741-08 U_G741-08 0 0 2 -9 G G G G T T C C
but technically it does not have to obey that formatting to be valud.