switch genders or gender?

Solution 1:

We also say, in American English, at least, that people switch sides when they change their position about an issue or switch parties when they, as Charlie Crist, former GOP governor of Florida, just did by becoming a Democrat. Switched genders is, according to Google Ngrams, a little more frequent than switched gender. It's probably because there are two sides, two major political parties, usually two opinions (pro and anti) about big issues, and two genders. However, both are grammatically and semantically correct. It's a style preference and not a grammar problem.