鱼类粗线期二价体上染色粒的研究

Chromomere Study on Fish Pachytene Bivalents

在红鲫减数分裂不同时相粗线期二价体上都可看到清晰度各不相同的染色粒带．在早粗线期，二价体上的染色粒过于细小，染色粒分布式样的特征难以分辨．随着二价体的收缩，染色粒因融合而变粗，数目减少，分布式样的特征性也逐渐明显．到晚粗线期，除少数已经局部分离的二价体外，大多数二价体都显示了特征明显，光反差良好的染色粒带．收缩程度基本一致的相应二价体上，染色粒带型和带数也一致．当染色粒减少到某一定数目后，染色粒不再相互融合．因此，染色粒带可作为区分鱼类染色体和染色体片段，分析染色体结构变异的可靠标识．

Chromomeres in varying degrees of clearness were observed on early, middle and late pachytene bivalents in red crucian carp, Carassius auratus. At early stage, chromomeres were too small to be distinguished well. Along with contraction of the bivalents, chromomeres became bigger and fewer in number by fusions. At middle stage, definit bivalent specific chromomere patterns appeared and a centromere that stained darker than the other chromomeres was observed on every bivalent. In late pachytene spermatocyte, except some bivalents which had been partly separated, most of the bivalents showed sharply defined bivalent specific chromomere patterns. Corresponding bivalents which contracted almost at the same degree showed both same chromomere pattern and number. Fusions of chromomeres did not continue when chromomeres reduced to a certain number even though the bivalents were continuing to contract more. These results suggest that chromomeres may be used as landmarks to identify a spcific bivalent in fish.