Terminal logging
 

In order to make the .bash_probfile read on login, is it better to longin to xterminal with -login option? I am using gnome desktop.

Welcome to LQ
I don't think it matters

If you've got bash set as your login shell in /etc/passwd, it'll read it automatically (& .bashrc if its there)

As Chris said, simply change your login shell in /etc/passwd file, then logout and login again so the shell will automatically read your ~/.bashrc or ~/.profile file.

However, explain the issue little more for specific answers.

If you want to have an existing shell session reflect any changes you've made in your shell config file(s), you can always simply source the config file(s), as they are simply shell scripts:
This removes the need to log out & log in. You would need to do this for each currently open shell session.

--- rod.

Little correction. In order to avoid sourcing the ~/.bashrc everytime you login, better change your login shell in /etc/passwd, so you won't need to source the file.

Edit the /etc/passwd file, and make change like this:

You completely missed my point. For existing shell sessions, you don't need to log out and then login again; simply source the startup script to pull in the changes. I've even seen people recommend to reboot the host in order for their changes to take effect. This is completely un-necessary.
--- rod.