A phenomenon in spoken Arabic

There are some foreign words,that enter to the spoken Arabic and we give it a feminine form. like the Loanword:”doctor”  becomes “doctora” in feminine form.And there’s Loanwords that do not change in the both forms like: “DJ”. In this research i want to examine why native speakers of Arabic do this to some words and don’t with some others and looking at what kind of agreement we get with such words. Think of sentences like the following:

1. The doctor/DJ arrived.

2. I saw the new doctor/DJ.

3. The new doctor/DJ arrived.

Does the adjective or the verb inflect according to the natural (semantic) gender? Is it different from what happens with native Arabic words?