Genética literally means "genetics," referring to the biological study of heredity. It's a word you wouldn't typically expect to find in a romantic pop song.
However, Camilo uses it in a unique and intriguing way, singing, "Quiero saber qué es lo que tiene tu genética" (I want to know what your genetics have). This line playfully suggests that his attraction is so profound, it must be rooted in something fundamental and irresistible about the other person's very being, making it a memorable and enticing word choice.
This song is one big, hilarious exaggeration about how lovesick someone can be. Camilo and Camila Cabello sing about feeling so physically overwhelmed by desire that it's become a full-blown medical emergency. He's not getting out of bed, not because he's sick, but because "las sábanas huelen a ti" [the sheets smell like you]. He's got a fever, his heart is about to explode, and his blood pressure is dangerously high.
He takes this idea and runs with it, telling you that if you see emergency services, they're probably heading to his place. "Si ven una ambulancia o un policía / Seguro que están yendo para la casa mía" [If you see an ambulance or a police car / They're surely going to my house]. He even called the fire department himself because after one night with this person, his bed "Sigue prendida en fuego" [Is still on fire]. It's a super fun and over-the-top way to describe a burning passion that has completely taken over.