The pattern of the colors is controlled by the speed of the egg as it passes through the uterus and the degree of turning it undergoes while passing through.

이 문장에서  the degree of turning it 뒤의 undergoes 라는 동사가 어떻게 등장하게 된 것인가요?

by the speed of the egg 와 the degree of turning it 이 짝을 이룬다는 것은 파악했습니다.