Glazier Douglas S
Department of Biology, Juniata College, Huntingdon, PA 16652, USA.
Biology (Basel). 2021 Mar 26;10(4):270. doi: 10.3390/biology10040270.
The body size and (or) complexity of organisms is not uniformly related to the amount of genetic material (DNA) contained in each of their cell nuclei ('genome size'). This surprising mismatch between the physical structure of organisms and their underlying genetic information appears to relate to variable accumulation of repetitive DNA sequences, but why this variation has evolved is little understood. Here, I show that genome size correlates more positively with egg size than adult size in crustaceans. I explain this and comparable patterns observed in other kinds of animals and plants as resulting from genome size relating strongly to cell size in most organisms, which should also apply to single-celled eggs and other reproductive propagules with relatively few cells that are pivotal first steps in their lives. However, since body size results from growth in cell size or number or both, it relates to genome size in diverse ways. Relationships between genome size and body size should be especially weak in large organisms whose size relates more to cell multiplication than to cell enlargement, as is generally observed. The ubiquitous single-cell 'bottleneck' of life cycles may affect both genome size and composition, and via both informational (genotypic) and non-informational (nucleotypic) effects, many other properties of multicellular organisms (e.g., rates of growth and metabolism) that have both theoretical and practical significance.
生物体的体型和（或）复杂性与其每个细胞核中所含遗传物质（DNA）的量（“基因组大小”）并非呈均匀相关。生物体的物理结构与其潜在遗传信息之间这种惊人的不匹配似乎与重复DNA序列的可变积累有关，但这种变异为何会进化却鲜为人知。在这里，我表明在甲壳类动物中，基因组大小与卵大小的正相关性比与成体大小的正相关性更强。我解释说，在其他动植物中观察到的这种及类似模式，是由于在大多数生物体中基因组大小与细胞大小密切相关，这也适用于单细胞卵和其他细胞数量相对较少的生殖繁殖体，而这些是它们生命中关键的第一步。然而，由于体型是由细胞大小或数量或两者的增长所导致的，所以它与基因组大小的关系是多样的。正如普遍观察到的那样，在体型更多与细胞增殖而非细胞增大相关的大型生物体中，基因组大小与体型之间的关系应该特别弱。生命周期中普遍存在的单细胞“瓶颈”可能会影响基因组大小和组成，并且通过信息（基因型）和非信息（核型）效应，还会影响多细胞生物体的许多其他特性（例如生长和代谢速率），这具有理论和实际意义。
