The influence of chromosome content on the size and shape of sperm heads in Drosophila melanogaster and the demonstration of chromosome loss during spermiogenesis.
The influence of chromosome content on the size and shape of sperm heads in Drosophila melanogaster and the demonstration of chromosome loss during spermiogenesis.
复制标题
染色体含量对果蝇精子头大小和形状的影响以及精子发生过程中染色体丢失的证明。
作者：
R. Hardy
精子头的体积是通过对近成熟的精子细胞核连续切开的束进行三维重建来估计的。所有精子染色质含量相同(X/Y和1n(3LR)/+)的雄性包囊的核体积呈单峰频率分布，而减数分裂分离可能将不同数量的染色质物质输送到精子细胞核的雄性包囊则显示两种或更多(T(2；3)/+和C(2L)；C(2R))模式。在这些病例中，亚群的平均体积与其染色体补体的中期长度的比例相同。因此，精子核的体积与其DNA含量成正比。另一方面，精子头形状似乎对染色体构成不是很敏感，因为不同大小的头在形状上没有太大的差异。-一个囊中不同大小类别的精子头的数量与孟德尔的预期不同；这些偏离是由于在个性化过程中，在第二次减数分裂结束时在精子细胞中形成的微核内的染色体被消除所造成的。这种染色体丢失的影响是增加了精子池中无体配子的比例。-根据体积测量估计了XY-O型男性中携带XY和nullo-X、nullo-Y精子的相对频率。将这一估计作为受精人口的衡量标准，可以从受精后性别比例随时间的变化推断出，在离开雌性受精器进行卵子受精方面，携带XY的精子比Nullo-X、nullo-Y精子优势1.5倍。
The volumes of sperm heads were estimated from three-dimensional reconstructions of serially sectioned bundles of nearly mature spermatid nuclei. Cysts from males in which all sperm are expected to have comparable amounts of chromatin (X/Y and 1n(3LR)/+) show unimodal frequency distributions of nuclear volumes, whereas cysts from males in which meiotic segregation is expected to deliver unequal amounts of chromatin material to spermatid nuclei show two (XY/O and XY/Y) or more (T(2;3)/+ ANd C(2L);C(2R)) modes. The mean volumes of the subpopulations in these cases are related in the same proportions as the metaphase lengths of their chromosomal complements. Thus the volumes of sperm nuclei are proportional to their DNA content. Sperm head shape, on the other hand, does not appear to be very sensitive to chromosomal constitution, as heads of different size do not vary greatly in shape.----The numbers of sperm heads in the various size classes in a cyst depart from mendelian expectations; these departures are caused by the elimination, during individualization, of chromosomes contained within micronuclei that are formed in spermatids at the end of the second meiotic division. The effect of this chromosome loss is to increase the proportion of nullosomic gametes in the sperm pool.----The relative frequencies of XY-bearing and nullo-X, nullo-Y sperm in XY/O males were estimated from the volume measurements. Taking this estimate as a measure of the fertilizing population, it is possible to infer from the change in sex ratio over time following insemination, that XY-bearing sperm have an advantage of 1.5 over nullo-X, nullo-Y sperm in leaving the seminal receptacle of the female for fertilization of ova.