This is the revolutionary new tool that's taking neuroscience by storm, and in this case, "opto" means light and "genetic" refers to the fact that these fruit flies have been modified to contain a special gene that makes only certain neurons respond to light.
a nova ferramenta revolucionária que está popularizando a neurociência. Neste caso, "opto" significa luz, e "genética" refere-se ao fato de essas moscas terem sido modificadas para conter um gene especial que faz apenas certos neurônios reagirem à luz.