Using jQuery/JSON populate drop downs and provide add/remove functionality

ALSO required knowledge of JSON I'm building a web app, this project is to write the functionality for one part of it. 3 drop downs are populated from a JSON request. The goal is to prepare another JSON POST request. There are 3 parts to this, 2 of these parts are done, 1 is not. This project is to do this final part. A user will be able to select game genre(s), by default the children of that genre will be added into the JSON request. Simple. However what is required is the functionality to remove games from the request as well as add games from other genres into the request. It will also include adding grouping to a drop down menu. The drop downs are currently bootstrap select pickers, allowing multiple options to be selected at the same time, this must be used for the 'new' functionality too. This must be done using jquery and HTML. I will provide all the required documents, including mockups and requirements as well as the current application. Thanks