Moran P, Martinez J L, Garcia-Vazquez E, Pendas A M
Departamento de Biología Funcional, Universidad de Oviedo, Spain.
Cytogenet Cell Genet. 1996;75(2-3):145-50. doi: 10.1159/000134466.
The karyotype of the rainbow trout is characterized by a primitive XX/XY sex-determining chromosomal system. (Thorgaard et al., 1977). In the present study using FISH we have physically linked the 5S rRNA genes to the partially undifferentiated X chromosome pair. PCR amplified 5S rDNA was used for FISH and hybridization signals indicated that the genes were duplicated, present in one acrocentric and one metacentric pair of chromosomes. After analyzing several individuals, the female metaphases showed four fluorescent signals whereas males presented only three signals. Two of the three signals obtained in males corresponded to the metacentric pair whereas the single signal was mapped to the heterochromatin that cytologically differentiates the X chromosome from the Y chromosome. Double FISH experiments demonstrated that the 5S rDNA which is not sex linked is located at the NOR bearing arm close to the major ribosomal RNA genes (5.8S, 18S and 28S), similar to the situation observed in Atlantic salmon (Pendas et al., 1994a).
虹鳟鱼的核型以原始的XX/XY性别决定染色体系统为特征。（索尔加德等人，1977年）。在本研究中，我们使用荧光原位杂交（FISH）技术将5S rRNA基因物理定位到部分未分化的X染色体对上。PCR扩增的5S rDNA用于FISH，杂交信号表明这些基因是重复的，存在于一对近端着丝粒染色体和一对中着丝粒染色体上。在分析了多个个体后，雌性中期细胞显示出四个荧光信号，而雄性仅呈现三个信号。雄性获得的三个信号中的两个对应于中着丝粒对，而单个信号则定位到从细胞学上区分X染色体和Y染色体的异染色质上。双重FISH实验表明，不与性别连锁的5S rDNA位于靠近主要核糖体RNA基因（5.8S、18S和28S）的核仁组织区（NOR）臂上，这与在大西洋鲑中观察到的情况类似。（彭达斯等人，1994a）
