1987年,由Selker等在粗糙脉孢菌中首次发现重复序列诱导点突变(repeat-induced point mutation,RIP).在重复序列诱导点突变过程中,搜寻前减数分裂组织单倍体核中DNA的重复序列,然后发生众多的碱基C到T的突变,产生富碱基T+A片段,从而使...1987年,由Selker等在粗糙脉孢菌中首次发现重复序列诱导点突变(repeat-induced point mutation,RIP).在重复序列诱导点突变过程中,搜寻前减数分裂组织单倍体核中DNA的重复序列,然后发生众多的碱基C到T的突变,产生富碱基T+A片段,从而使重复序列中的G-C碱基对发生转换突变成为A-T碱基对.此外,发生RIP的序列多集中在着丝粒区域,主要是转座子甲基化后的遗迹.移动转座子是真核生物基因组进化的主要驱动力.对于真菌,重复序列诱导点突变(RIP)在减数分裂过程中通过突变多拷贝DNA,能最大限度地减少转座子的影响,因此对RIP的研究在一定程度上能有助于了解基因组进化的真谛.综述了重复序列诱导点突变的产生机制,以及真菌中重复序列诱导点突变的研究进展.展开更多
Context: Currently, fetal point mutations cannot be reliably analyzed from circulatory fetal DNA in maternal plasma, due to the predominance of maternal DNA sequences. However, analysis of circulatory fetal DNA sequen...Context: Currently, fetal point mutations cannot be reliably analyzed from circulatory fetal DNA in maternal plasma, due to the predominance of maternal DNA sequences. However, analysis of circulatory fetal DNA sequences in maternal plasma have been shown to selectively enrich for fetal DNA molecules on the basis of a smaller molecular size than maternal DNA. Abstract Objective: To examine the prenatal analysis of 4 common β - thalassemia point mutations: IVSI- 1, IVSI- 6, IVSI- 110, and codon 39. Design, Setting, and Patients: A total of 32 maternal blood samples were collected at 10 to 12 weeks of gestation (mean, 10.7 weeks) between February 15, 2003, and February 25, 2004, in Bari, Italy, from women with risk for β - thalassemia in their newborns immediately prior to chorionic villous sampling. Samples in which the father and mother did not carry the same mutation were examined. Circulatory DNA was size- fractionated by gel electrophoresis and polymerase chain reaction (PCR) amplified with a peptide- nucleic- acid clamp, which suppresses amplification of the normal maternal allele. Presence of the paternal mutant allele was detected by allele- specific real- time PCR. Main Outcome Measure: Detection of paternally inherited β - globin gene point mutations. Results: Presence or absence of the paternal mutant allele was correctly determined in 6 (86% ) of 7 cases with the IVSI- 1 mutation, 4 (100% ) of 4 with the IVSI- 6 mutation, 5 (100% ) of 5 with the IVSI- 110 mutation, and 13 (81% ) of 16 with the codon 39 mutation. One false- positive test result was scored for the IVSI- 1 mutation. Two cases with the codon 39 mutation were classified as uncertain and 1 case was excluded due to lack of a diagnostic test result at the time of analysis. These results yielded an overall sensitivity of 100% and specificity of 93.8% , with classified cases removed. Conclusion: Our recently described technique of the size- fractionation of circulatory DNA in maternal plasma may be potentially useful for the noninvasive prenatal determination of fetal point mutations.展开更多
文摘1987年,由Selker等在粗糙脉孢菌中首次发现重复序列诱导点突变(repeat-induced point mutation,RIP).在重复序列诱导点突变过程中,搜寻前减数分裂组织单倍体核中DNA的重复序列,然后发生众多的碱基C到T的突变,产生富碱基T+A片段,从而使重复序列中的G-C碱基对发生转换突变成为A-T碱基对.此外,发生RIP的序列多集中在着丝粒区域,主要是转座子甲基化后的遗迹.移动转座子是真核生物基因组进化的主要驱动力.对于真菌,重复序列诱导点突变(RIP)在减数分裂过程中通过突变多拷贝DNA,能最大限度地减少转座子的影响,因此对RIP的研究在一定程度上能有助于了解基因组进化的真谛.综述了重复序列诱导点突变的产生机制,以及真菌中重复序列诱导点突变的研究进展.
文摘Context: Currently, fetal point mutations cannot be reliably analyzed from circulatory fetal DNA in maternal plasma, due to the predominance of maternal DNA sequences. However, analysis of circulatory fetal DNA sequences in maternal plasma have been shown to selectively enrich for fetal DNA molecules on the basis of a smaller molecular size than maternal DNA. Abstract Objective: To examine the prenatal analysis of 4 common β - thalassemia point mutations: IVSI- 1, IVSI- 6, IVSI- 110, and codon 39. Design, Setting, and Patients: A total of 32 maternal blood samples were collected at 10 to 12 weeks of gestation (mean, 10.7 weeks) between February 15, 2003, and February 25, 2004, in Bari, Italy, from women with risk for β - thalassemia in their newborns immediately prior to chorionic villous sampling. Samples in which the father and mother did not carry the same mutation were examined. Circulatory DNA was size- fractionated by gel electrophoresis and polymerase chain reaction (PCR) amplified with a peptide- nucleic- acid clamp, which suppresses amplification of the normal maternal allele. Presence of the paternal mutant allele was detected by allele- specific real- time PCR. Main Outcome Measure: Detection of paternally inherited β - globin gene point mutations. Results: Presence or absence of the paternal mutant allele was correctly determined in 6 (86% ) of 7 cases with the IVSI- 1 mutation, 4 (100% ) of 4 with the IVSI- 6 mutation, 5 (100% ) of 5 with the IVSI- 110 mutation, and 13 (81% ) of 16 with the codon 39 mutation. One false- positive test result was scored for the IVSI- 1 mutation. Two cases with the codon 39 mutation were classified as uncertain and 1 case was excluded due to lack of a diagnostic test result at the time of analysis. These results yielded an overall sensitivity of 100% and specificity of 93.8% , with classified cases removed. Conclusion: Our recently described technique of the size- fractionation of circulatory DNA in maternal plasma may be potentially useful for the noninvasive prenatal determination of fetal point mutations.
