This procedure was recently written up by a gentleman who goes by the name of Sumac on the several evolution discussion boards where he originally posted this material. He has given me permission to reproduce his post. This process will allow you to demonstrate that the vast majority (all?) of DNA that has been sequenced in both humans and chimpanzees are the same at 96% - 100% of the nucleotide sites.
Pick a sequence at random and open the page to view the sequence and
accompanying information. Select and copy the DNA sequence (typically,
the DNA sequence is at the bottom of the page). At this point, you
can paste the sequence into a word processor program to remove spaces and
digits or go directly to the next step; BLAST should ignore the spaces
and digits, but I don't know if it always does.
Go to NCBI BLAST and choose Basic BLAST. BLAST is a program that searches the databases for similar sequences. Paste the copied sequence into the search field box. The default settings (blastn, non-redundant database, FASTA format, etc.) are sufficient for this demonstration Click the 'search' button.
The next page you get will give you a request ID number for your search. Click the 'format results' button. A new window will open with your search results
You should now have a page that contains a graphical representation of the search, a list of hits in order of similarity, and a sequence alignment for each hit. The first sequence in the hit list should be the original chimpanzee sequence. The first non-chimpanzee sequence will be human. Scroll down the page (or click the linked score to the right of the gene name) and look at the alignment for that sequence. The sequence identity will be somewhere between 96% and 100%. If you do a few of these searches and average out the similarities, you will find that the average identity between chimp and human will be very close to 98%.