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染色体脆点(fragile sites)是近年来新发现的一个细胞遗传学现象,它丰富了人类遗传变异库。自1965年首次发现脆点以来,迄今共发现17个罕见的遗传性脆点。根据它们表现所需的培养基条件,可以把脆点分为三类:第一类是叶酸敏感的脆点,有2q11、2q13、6p23、7p11、8q22、9p21、9q32、10q23、11q13、11q23、12q13、16p12、20p11和Xq27。所有这些脆点的表现要求培养基中缺乏叶酸和胸苷。第二类脆点对叶酸不敏感,可在培养基中自发地表现,伹最近证明可用远霉素A、BUdR等诱导,这一类脆点为16q22和17p12。第三类脆点10q25
The fragile sites are a newly discovered cytogenetic phenomenon in recent years, which enriches the human genetic variation database. Since the first discovery of brittle spots in 1965, a total of 17 rare hereditary brittle points have been discovered so far. According to the conditions of the media required for their performance, brittle points can be divided into three categories: The first type is folate-sensitive brittle, with 2q11, 2q13, 6p23, 7p11, 8q22, 9p21, 9q32, 10q23, 11q13, 11q23, 12q13, 16p12, 20p11 and Xq27. The performance of all these fragility points requires the lack of folic acid and thymidine in the medium. The second type of brittleness is not sensitive to folic acid and can be expressed spontaneously in the culture medium. The cockroach has recently been shown to be induced by the use of faromycin A, BUdR, etc. This type of brittleness is 16q22 and 17p12. The third type of brittle 10q25