With the advance of genetic mapping and comparin g of different genomes,an undiscovered type of conservation was revealed: the co nservation of gene content and gene orders on the genome level.

• 随着遗传作图的不断发展，人们开始比较不同物种的基因组，并且揭示了一种从未被发现的基因组水平上基因排列顺序的保守性。