By performing var_dump($wp_scripts->registered['jquery']), I noticed that this script has for dependency 'jquery-core'.
But according to the codex of the wp_register_script() function, this handle 'jquery-core' has the path /wp-includes/js/jquery/jquery.js
http://codex.wordpress.org/Function_Reference/wp_register_script
Is it normal that 'jquery' has for dependency 'jquery-core', which seems to be himself, if I have understood correctly?
Sorry for my english i use a translator.