Repetitive regions like 'AAAAAAA' or etc. obscure the meaningful outputs. So, in every search many of meaningless repetitive frames are eliminated.
Bases located at "blank" are masked with "N" means any of ATGC could be here but we don't care. Blank can also be choosen as 0, zero.
Steps are considered as places where the feet of protein located. Except "blank" part no mismatch are allowed for steps