Abstract
The findings of this research indicate that it is important for teachers to be aware of students' concepts in genetics before they start teaching them. It also showed that once students had resolved any difficulty with the relationship between gene and allele, their performances in genetics showed a significant improvement. This research found that the use of a chromosome model as a conceptual challenge tool was a most effective way of resolving these difficulties, especially if teachers were aware of students' concepts, and had undergone some staff development in the model's use.