脆性位点是染色体上特异的未着色的裂隙或断裂点。一些脆点可在标准细胞培养条件下自身表达,而另一些则需要高度特异的条件。它们的细胞学表现呈多样化,包括裂隙、断裂、无着丝粒断片和三射体结构。这些区域的生物学意义仍未可知。它们与智力迟滞的发生有关也可能与癌的染色体结构重排有关。目前,根据脆性位点在人群中的相对发生率将其分为两大类:罕见或遗传型脆性位点(r-fra)以孟德尔显性方式遗传,人群中出现频率低,但可在多半中期相中表达。另一种常见或结构型脆性位点(c-fra),群体 Fragile sites are specific unstained fissures or breakpoints on the chromosome. Some fragile spots are self-expressed under standard cell culture conditions, while others require highly specific conditions. Their cytological manifestations are diverse, including fissures, breaks, centromeric fragments, and triplet structures. The biological significance of these areas remains unknown. They are related to the occurrence of mental retardation and may also be related to the chromosomal rearrangement of cancer. Currently, according to the relative incidence of fragile sites in the population, they are divided into two categories: rare or genetically fragile sites (r-fra) are inherited in a Mendelian dominant manner, with a low frequency in the population but can be Mostly expressed in the middle phase. Another common or structural fragile site (c-fra), population