I have updated desktop computer to Debian Jessie. After that I have quickly encountered an issue with GNOME Terminal, Midnight Commander and already assigned F1 and F10 function keys.
Solution
Open GNOME Terminal preferences.
Ensure that Enable the menu accelerator key (F10 by default) option is unset.
Switch to the Shortcuts tab.
Modify F1 shortcut that opens Help/Contents.
Additional notes
If you tried alternative way to access function keys inside Midnight Commander by pressing alt and number, then notice that Alt+0,Alt+1..Alt+9 are already assigned.