人类Xq27脆性位点系指X染色体长臂末端2区7、8两带之间或附近的一个特定位点。具有脆性位点的X染色体称为脆性X染色体,又称为标记X染色体。其主要特征:1.具有宽度不等的非染裂隙,常涉及两个染色单体;2.恒定地出现在受检染色体的同一位置上;3.呈孟德尔式共显性遗传;4.具有明显的脆性。在体外适宜培养条件下,可出现无着丝粒片段、缺失或三射体图象。 Human Xq27 fragile locus refers to a specific site between or near the two regions 7 and 8 of the long arm of the X chromosome. The X chromosome with a brittle site is called the fragile X chromosome, also known as the labeled X chromosome. Its main features: 1. Has a width ranging from non-dye fissures, often involving two dichroic monomers; 2. Constantly appear in the same position on the chromosomes; 3. Mendelian co-dominant inheritance; Has obvious brittleness. In vitro culture conditions, there may be no centromeric fragments, missing or three-ray images.