[Chimera-users] chain selection in a multi-conformatin pdb file.

Hi Chimera fans, 1. If a pdb file contains more then one struture, how can I select and keep just one and get rid of the rest. Such as 1X95. It is a big mess after Chimera load the the DNA pdb structure. How can I leave just one double helix? 2. Can Chimera do the extension of DNA. Such as 1X95 has the hexamer with the sequence of ATGCAT, can Chimera double it to a dodecamer with a sequence ATGCATATGCAT? It Chimera can not do that, do you know which software has such a function. I tried PyMol but did not get what I wanted. Thanks a lot. Hong