Departamento de Genética, Facultad de Ciencias, Universidad de Granada, 18071, Granada, Spain.
Chromosome Res. 2022 Sep;30(2-3):217-228. doi: 10.1007/s10577-022-09692-7. Epub 2022 Jun 3.
Selfish genetic elements (SGE) get a transmission advantage (drive) thanks to their non-Mendelian inheritance. Here I identify eight steps during the reproductive cycle that can be subverted by SGEs to thrive in natural populations. Even though only three steps occur during meiosis, most cases of segregation distortion are considered "meiotic drive sensu lato." As this is a source of unnecessary contradictions, I suggest always using the term "transmission ratio distortion" (TRD). Chromosomal SGEs (e.g., B chromosomes) exhibit almost all types of TRD. In plants, the best-studied type of TRD for B chromosomes occurs post-meiotically during male gametophyte maturation. However, in animals, the two main types are pre-meiotic and meiotic TRDs, in all cases associated with gonotaxis (i.e., a preference of B chromosomes for germ cells). Frequently, TRD drivers in genic SGEs (e.g., t-alleles and segregation distorters in Drosophila) are paralogous copies of genes from the standard genome, whereas their targets can be other genes or satellite DNA (satDNA). As B chromosomes are often rich in satDNA and contain paralogous copies of A chromosome genes, perhaps their drive mechanisms are similar to those of genic SGEs. So far, the only association between a B chromosome gene and TRD is the gene haplodizer in Nasonia vitripennis. The discovery of B-genes controlling B-drive in other species does not appear to be far off, but experimental crosses will be needed to simultaneously test the TRD of a given B chromosome and the expression of its genes.
自私遗传元件 (SGE) 由于其非孟德尔遗传而获得传播优势（驱动）。在这里，我确定了生殖周期中的八个步骤，SGE 可以通过这些步骤在自然种群中茁壮成长。尽管只有三个步骤发生在减数分裂中，但大多数分离失真情况都被认为是“广义减数分裂驱动”。由于这是不必要矛盾的来源，我建议始终使用“传递率失真”（TRD）一词。染色体 SGE（例如 B 染色体）表现出几乎所有类型的 TRD。在植物中，B 染色体发生的最受研究的 TRD 类型发生在减数分裂后，在雄性配子体成熟过程中。然而，在动物中，两种主要类型是减数分裂前和减数分裂 TRD，在所有情况下都与 gonotaxis（即 B 染色体对生殖细胞的偏好）相关。TRD 驱动因子通常在基因 SGE（例如果蝇中的 t-等位基因和分离干扰因子）中是标准基因组基因的同源拷贝，而它们的靶标可以是其他基因或卫星 DNA（satDNA）。由于 B 染色体通常富含 satDNA 并包含 A 染色体基因的同源拷贝，因此它们的驱动机制可能与基因 SGE 的驱动机制相似。到目前为止，与 B 染色体基因和 TRD 唯一相关的是 Nasonia vitripennis 中的 haplodizer 基因。在其他物种中发现控制 B 驱动的 B 染色体基因似乎并不遥远，但需要进行实验杂交，以同时测试给定 B 染色体的 TRD 和其基因的表达。
