Joomla Registration form: Front end option to choose user group to register in

I have a free and open forum website where there are two categories of users: (i) Lawyers and (ii) non-Lawyers.

I want that while registering, the registration form should display two radio buttons showing the two user groups. The user will have an option to choose one of the two options (required), and the user will be registered in that group only.

At backend, I can set which user groups to be displayed in frontend.