ATGCU are neither alleles or aminoacids these are the nitrogenous bases present in DNA and RNA every living organism's DNA has ATGC and RNA has AUGC three nitrogenous bases make some sort of code for a aminoacid and manyaminoacids make protein which give certain characters called traits. mutation is actually certain abbretiations in these nitrogenous bases by agents such as physical or chemical no offence please i just wrote what i knew but i may be wrong yes different ethnic communities may have certain differences in their DNA structures due to polymorphisms which called RFLP and can be determined by doing PCR and gel electrophoresis.