多物种减数分裂中基因转换的研究

发布时间：2018-01-07 17:13

本文关键词：多物种减数分裂中基因转换的研究　出处：《南京大学》2017年博士论文　论文类型：学位论文

【摘要】：减数分裂中的基因转换可以打破基因组中局部的连锁不平衡,而且基因转换中具有GC偏好性,这一效应具有干扰检验自然选择的潜在可能,一直以来该效应也用于解释重组率与GC含量的正相关性。然而,这些效应影响力的大小取决于基因转换的频率和GC偏好性的大小。由于对基因转换的研究存在较大的技术难度,基因转换的频率和GC偏好性的大小现在都不明确。为了解决这些问题,在研究中我们对酵母、脉孢菌、衣藻和拟南芥的减数分裂产物进行了大规模的全基因组测序。结果表明,基因转换的频率(被转换碱基的比例)在不同物种中有超过三个数量级的差异,在酵母中约有2%的碱基被转换,而在衣藻和拟南芥中只有～0.005%的碱基被转换。如此大的差异的原因之一是不同物种本身重组率就存在差异,该差异与染色体的数目有关。同时,基因转换的长度也是造成差异的原因之一。基因转换的长度在不同物种中有显著差异,而且在CO-GC和NCO-GC间也有差异。我们在三个物种中检测到了重组率与GC含量的正相关性,但是在所有的物种中都没有检测到基因转换的GC偏向性。最后我们在脉孢菌中检测到了两个与重组事件紧密相关的序列模体,这是在哺乳类生物之外第一次检测到如此显著的序列模体。本研究证明了基因转换的频率在不同物种中存在很大差异,而且其GC偏好性很可能不是在所有物种中普遍存在的。
[Abstract]:Meiotic gene conversion can break the genome of local linkage disequilibrium, and gene conversion GC preference, this effect has the potential to interfere with the test of natural selection, since the effect is also used to explain the positive correlation between recombination rate and GC content. However, this effect depends on gene conversion the frequency of GC and preference of size. Because of the difficult technical research of gene transformation, gene conversion frequency and GC preference size are not clear. In order to solve these problems, in our study of yeast, Neurospora, Chlamydomonas and Arabidopsis meiosis cleavage products were whole genome sequencing large scale. The results showed that the gene conversion frequency (converted base ratio) in different species are more than three orders of magnitude difference in yeast, about 2% of the base was transferred Change, in Chlamydomonas and Arabidopsis only ~ 0.005% base conversion. One reason for such a great difference is there between different species recombination rate, the number of differences with the chromosome. At the same time, the length of gene conversion is one of the reasons causing the differences. There are significant differences among different species, gene conversion the length, but there are differences in CO-GC and NCO-GC. We got to the positive correlation between recombination rate and GC were detected in three species, but in all species are not detected by gene conversion GC bias. Finally we in Neurospora was detected in two and recombination events are closely related the motif, which is in addition to mammals first detected sequence motifs so significant. This study demonstrated that the gene conversion frequency in different species, and the preference is GC Can not be common in all species.

【学位授予单位】：南京大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：Q75

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