Phillips R B, Ihssen P E
Cytogenet Cell Genet. 1985;39(1):14-8. doi: 10.1159/000132097.
In the male trout there is a difference in the quinacrine banding and C-banding patterns between the two homologs of the second largest chromosome pair. This chromosome is the only large submetacentric in the karyotype, making it easy to identify and suggesting that the sex chromosomes have become differentiated since the time of tetraploidization. In males one homolog has a medium-to-large quinacrine bright heterochromatic band on the end of the short arm, while the other lacks it completely. In females both homologs have medium-to-large quinacrine bright heterochromatic bands. Approximately half the progeny from every lake trout cross studied and half the eggs from every lake trout population examined were heteromorphic for a difference in this chromosome band. Results from sexed fish, reciprocal F1 hybrids between brook trout and lake trout, and gynogenetic haploids are all consistent with the interpretation that chromosome 2 is the sex chromosome. These results suggest that the addition of heterochromatin to the X can be the first step in the inhibition of crossing over between the X and Y chromosomes required for sex chromosome differentiation.
在雄性虹鳟中，第二大染色体对的两个同源染色体之间的喹吖因带型和C带型存在差异。这条染色体是核型中唯一的大型亚中着丝粒染色体，易于识别，这表明自四倍体化以来性染色体已经分化。在雄性中，一个同源染色体在短臂末端有一条中等至大型的喹吖因亮异染色质带，而另一个则完全没有。在雌性中，两个同源染色体都有中等至大型的喹吖因亮异染色质带。在所研究的每条湖鳟杂交后代中，约一半以及所检测的每个湖鳟种群的约一半卵，在这条染色体带的差异上是异态的。性成熟鱼、溪鳟和湖鳟之间的正反交F1杂种以及雌核发育单倍体的结果均与2号染色体是性染色体这一解释一致。这些结果表明，在X染色体上添加异染色质可能是性染色体分化所需的X和Y染色体之间交叉抑制的第一步。
