I would like to generate a tree based on multiple DNA sequence alignment from ClustalW. I have not trimmed my sequences, but under the default ClustalW setting, does it only calculate the similarities on the region where all sequences are aligned? In another words, if I have some sequences that are longer than others, will these regions be calculated as gaps?
I have posted an image of my alignment for visual aid: will the gap seen in sequence 2/1-829 be seen as differing from the other 3 sequences?
Thanks for any input.














