Enforced: The author wants to show that smart and hot are not mutually exclusive.
Lampshaded: "And my hot biology professor, Dr. Smartypants..."
Invoked: Dr. Smartypants works hard to maintain her appearance to prove that just because she's intelligent does not mean that she can't be beautiful, too.
Exploited: Because Dr. Smartypants is meeting with the press/board of directors/investors/Congress, she makes an effort to clean up her appearance in hopes of getting more funding or publicity for her research.
Discussed: "Remember, we're going to meet Dr. Smartypants tomorrow; twenty bucks says she's way hot."
Conversed: "They're getting such hot actors to play scientists these days. It's like they care more about the character's appearance than her actual scientific credentials."
Deconstructed: Others may not take Dr. Smartypants seriously, because her profession cares about smarts, not looks. Other scientists may write her off as a Brainless Beauty, which forces Dr. Smartypants to have to work twice as hard as her colleagues to get credit where it's due.
Reconstructed: But because Dr. Smartypants has to work harder, she's very dedicated to what she does, and her work is outstanding. Which eventually does lead to her winning the respect and admiration of the other scientists.