Instituto de Ecología, Genética y Evolución (IEGEBA)-Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET) and Laboratorio de Citogenética y Evolución (LaCyE), Departamento de Ecología, Genética y Evolución, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Autónoma de Buenos Aires, Argentina.
Instituto de Ecología, Genética y Evolución (IEGEBA)-Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET) and Laboratorio de Citogenética y Evolución (LaCyE), Departamento de Ecología, Genética y Evolución, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Autónoma de Buenos Aires, Argentina
AoB Plants. 2014 Jun 26;6:plu029. doi: 10.1093/aobpla/plu029.
Evolutionary chromosome change involves significant variation in DNA amount in diploids and genome downsizing in polyploids. Genome size and karyotype parameters of Hippeastrum species with different ploidy level were analysed. In Hippeastrum, polyploid species show less DNA content per basic genome than diploid species. The rate of variation is lower at higher ploidy levels. All the species have a basic number x = 11 and bimodal karyotypes. The basic karyotypes consist of four short metacentric chromosomes and seven large chromosomes (submetacentric and subtelocentric). The bimodal karyotype is preserved maintaining the relative proportions of members of the haploid chromosome set, even in the presence of genome downsizing. The constancy of the karyotype is maintained because changes in DNA amount are proportional to the length of the whole-chromosome complement and vary independently in the long and short sets of chromosomes. This karyotype constancy in taxa of Hippeastrum with different genome size and ploidy level indicates that the distribution of extra DNA within the complement is not at random and suggests the presence of mechanisms selecting for constancy, or against changes, in karyotype morphology.
进化中的染色体变化涉及到二倍体中 DNA 数量的显著变化和多倍体中基因组的缩小。分析了不同倍性水平的火球属物种的基因组大小和核型参数。在火球属中，多倍体物种的每个基本基因组的 DNA 含量低于二倍体物种。在更高的倍性水平下，变异率较低。所有物种都具有基本数 x = 11 和双峰核型。基本核型由四条短着丝粒染色体和七条大染色体（亚着丝粒和亚端着丝粒）组成。双峰核型得以保持，维持了单倍体染色体组成员的相对比例，即使在基因组缩小的情况下也是如此。核型的恒定性得以维持，因为 DNA 数量的变化与整个染色体组的长度成正比，并且在长和短染色体组中独立变化。这种在具有不同基因组大小和倍性水平的火球属分类群中的核型恒定性表明，额外 DNA 在染色体组内的分布不是随机的，并且表明存在选择核型形态恒定性或反对变化的机制。
