Can I use a Time Machine Backup (on an external drive) as a "start up" drive? I need to do a disk repair.

I am upgrading my MacBook Pro (17"; Intel Core Duo; Speed 2.16 GHz; 2 GB 667MHz DDR2 SDRAM) from Leopard (10.5.8) to Snow Leopard (10.6.8). I successfully Time Machine to make a backup to an external LaCie drive. Some issues appeared when I ran a "disk verify," and need to change the startup drive to boot up and use "repair disk." When I tried to change the startup drive (in System Preferences) the drive with the Time Machine Backup was not recognized. Can I even use Time Machine to create a bootable drive? I use Carbon Copy Clone with my iMac (and can boot from the clone), but that is not an option when running OSX 10.5.8.