Heterozygosity, heteromorphy, and phylogenetic trees in asexual eukaryotes.
Heterozygosity, heteromorphy, and phylogenetic trees in asexual eukaryotes.
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无性真核生物中的杂合性、异形性和系统发育树。
DOI：
10.1093/genetics/144.1.427
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发表时间：
1996
期刊：
影响因子：
3.3
通讯作者：
BirkyJr,CW
中科院分区：
文献类型：
--
作者：
BirkyJr,CW
很少有人关注二倍体或多倍体真核生物长期无性繁殖对序列进化的影响。一些基本理论表明，无性个体中蛋白质编码基因的两个等位基因之间的中性序列差异量将比有性物种中的差异量大2tu倍，其中tu是无性繁殖丧失后的世代数，tu是无性谱系中每代的突变率。基于两个或两个以上物种中的每一个的一个等位基因的系统发育树将显示不正确的分歧时间，并且通常不正确的拓扑结构。这种等位基因序列差异可以通过有丝分裂基因转换、有丝分裂交换或倍性减少而暂时停止。如果这些聚合事件是罕见的，古代无性谱系可以通过它们的高等位基因序列分歧来识别。在中间频率的收敛事件，这将是不可能的重建正确的无性进化枝的蛋白质编码基因的序列。会聚可能受到等位基因序列趋异和杂合染色体重排的限制，杂合染色体重排降低了重组所需的同源性，并导致交换或倍性循环后的非整倍性。
Little attention has been paid to the consequences of long-term asexual reproduction for sequence evolution in diploid or polyploid eukaryotic organisms. Some elementary theory shows that the amount of neutral sequence divergence between two alleles of a protein-coding gene in an asexual individual will be greater than that in a sexual species by a factor of2tu, wheretis the number of generations since sexual reproduction was lost anduis the mutation rate per generation in the asexual lineage. Phylogenetic trees based on only one allele from each of two or more species will show incorrect divergence times and, more often than not, incorrect topologies. This allele sequence divergence can be stopped temporarily by mitotic gene conversion, mitotic crossing-over, or ploidy reduction. If these convergence events are rare, ancient asexual lineages can be recognized by their high allele sequence divergence. At intermediate frequencies of convergence events, it will be impossible to reconstruct the correct phylogeny of an asexual clade from the sequences of protein coding genes. Convergence may be limited by allele sequence divergence and heterozygous chromosomal rearrangements which reduce the homology needed for recombination and result in aneuploidy after crossing-over or ploidy cycles.