Finding Pattern in GENES

Question

[m_punisher6]

Hi all

I want to find same sequence DNA in one GENE through other GENES with exact length and exact miss match. I found BLAST and MUMMER tools for this work but I don't know how to determine the length of the pattern and the minimum and the maximum of mismatches.

I can work with BLAST but I have no idea with mummer.

Thanks

mansoor