tokens: Our findings revealed the following characteristics of the germ - line mutations of APC 1 ) the great majority of the mutations were found to truncate the APC product ; 2 ) almost all of the mutations were located within the first half of the coding region ; 3 ) no correlation was observed between the locations of germ - line mutations and extracolonic manifestations in FAP patients ; 4 ) more than 80 % of base substitutions in the APC gene were from cytosine to other nucleotides , nearly one - third of which occurred at the GpG site .