palato-alveolar affricate

Hi.

Can someone tell me, what is the sound of a voiced palato-alveolar
affricate ? Is this what English speakers think of as a "j" sound, as in
"jelly jar" ? Is it something else ?

Also, does it seem a reasonable sound change to have a palatalized g
become this sound ? And a palatalized k --> voiceless palato-alveolar
affricate ?

Thanks

David Stokes