In grade school, maybe you heard that one gene determines eye color, and the brown-eyed trait always dominates over the blue-eyed trait.

在小学你可能听说过一个基因决定着眼睛的颜色，而且棕色眼睛相比于蓝色眼睛是显性性状。

This allowed them to determine the genes that have allowed polar bears to survive in one of the toughest environments on Earth.

这使他们能够确定使北极熊能够在地球上最恶劣的环境之一中生存的基因。