Problem syncing iPhone 5 with iMac with Yosemite

Since upgrading my iMac to Yosemite I have found that I can't sync my iPhone 5 or my daughter's iPhone fully:

It syncs with iPhoto but fails to connect with iTunes - miniature multi- coloured cartwheel searches forever.

I therefore can't find a way of syncing music or of backing up my iPhone.

All suggestions that I've found in terms of ensuring latest versions of itunes and Yosemite ( done), of syncing using wifi ( can't because the iPhone doesn't link with iTunes), changing usb ( done -apple), rebooting (done) have failed!

Is there anyone who can offer a way forwards?