Anyone can edit Wikipedia, and your edits are preserved forever in the history of the page. Creating an account is very helpful for keeping track of the pages you edit, plus it is required for starting a new article. Create an account here or at the upper right of the Wikipedia main page.
Now that you've created an account, look up the topic of your research or dissertation. Try a few different search terms within Wikipedia (e.g. different gene names, or gene versus protein), as well as a Google search. You might be surprised at how little information is available. For example, podocalyxin appears in nearly 300 PubMed articles, but its Wikipedia article is just one paragraph long. Click the "Edit" tab to start adding information.
Rarely, there will be no Wikipedia entries at all relating to the topic of your expertise. This is a fantastic opportunity for you to add to mankind's body of knowledge. Wikipedia has a wizard for creating a new article which you can learn more about here.
Next: How to summarize your research effectively