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Xq27脆性部位与智力障碍有关,而其它脆性部位的影响作用仍不清楚。一种可能性是这些脆性部位与疾病根本无关,是既无利又无害的一种中性现象。另一种可能性是某些脆性部位具有选择性不利,容易引起自然流产或纯合子非致死性的损伤。第三种可能性是某些脆性部位易于引起染色体断裂。减数分裂过程中,脆性部位的断裂可能会在配子或胎儿中产生染色体重排,那么这些重排就会有反映,导致这些断裂的脆性位点的分布的断裂点。为此作者对羊膜穿刺中发现的导致染色体重排的278个断裂点的分
Xq27 fragile parts and mental retardation, while the impact of other fragile parts is still not clear. One possibility is that these fragile parts have nothing to do with the disease and are neither neutral nor harmless as a neutral phenomenon. Another possibility is that some of the fragile sites are selectively detrimental, easily lead to spontaneous abortion or homozygous non-fatal injury. A third possibility is that some of the fragile sites tend to cause chromosomal breaks. During meiosis, fragmentation at the fragile site may produce chromosomal rearrangements in the gamete or fetus, and these rearrangements are reflected, leading to breakpoints in the distribution of the fragile sites of these breaks. To this end the authors found amniocentesis in chromosomal rearrangements that resulted in 278 break points