Devlin R H, Stone G W, Smailus D E
Fisheries and Oceans Canada, Vancouver, B.C., Canada.
J Mol Evol. 1998 Mar;46(3):277-87. doi: 10.1007/pl00006304.
A long repetitive DNA sequence (OtY8) has been cloned from male chinook salmon and its genomic organization has been characterized. The repeat has a unit length of 8 kb and is present approximately 300 times per diploid male nucleus. All internal fragments within the 8-kb repeat segregate from father to son, suggesting that the entire repeat unit is located on the Y chromosome. The organization of this sequence into an 8-kb repeat unit is restricted to the Y chromosome, as are several male-specific repeat subtypes identified on the basis of restriction-site variation. The repeat possesses only weak internal sequence similarities, suggesting that OtY8 has not arisen by duplication of a smaller repeat unit, as is the case for other long tandem arrays found in eukaryotes. Based on a laddered pattern arising from partial digestion of genomic DNA with a restriction enzyme which cuts only once per repeat unit, this sequence is not dispersed on the Y chromosome but is organized as a head-to-tail tandem array. Pulse-gel electrophoresis reveals that the direct-tandem repeats are organized into at least six separate clusters containing approximately 12 to 250 copies, comprising some 2.4 Mb of Y-chromosomal DNA in total. Related sequences with nucleotide substitutions and DNA insertions relative to the Y-chromosomal fragment are found elsewhere in the genome but at much lower copy number and, although similar sequences are also found in other salmonid species, the amplification of the repeat into a Y-chromosome-linked tandem array is only observed in chinook salmon. The OtY8 repetitive sequence is genetically tightly associated with the sex-determination locus and provides an opportunity to examine the evolution of the Y chromosome and sex determination process in a lower vertebrate.
从雄性银大麻哈鱼中克隆出了一段长重复DNA序列（OtY8），并对其基因组结构进行了表征。该重复序列的单位长度为8 kb，每个二倍体雄性细胞核中大约存在300次。8 kb重复序列内的所有内部片段都从父本遗传给子代，这表明整个重复单元位于Y染色体上。该序列组织成8 kb重复单元的情况仅限于Y染色体，基于限制性酶切位点变异鉴定出的几种雄性特异性重复亚型也是如此。该重复序列仅具有微弱的内部序列相似性，这表明OtY8并非由较小重复单元的复制产生，真核生物中发现的其他长串联阵列就是这种情况。基于用一种每重复单元仅切割一次的限制性酶对基因组DNA进行部分消化产生的阶梯状模式，该序列并非分散在Y染色体上，而是组织成头对头的串联阵列。脉冲场凝胶电泳显示，直接串联重复序列被组织成至少六个单独的簇，包含大约12至250个拷贝，总共约2.4 Mb的Y染色体DNA。相对于Y染色体片段具有核苷酸替换和DNA插入的相关序列在基因组的其他地方也有发现，但拷贝数要低得多，并且尽管在其他鲑科鱼类中也发现了类似序列，但只有在银大麻哈鱼中观察到该重复序列扩增成与Y染色体相连的串联阵列。OtY8重复序列在遗传上与性别决定位点紧密相关，为研究低等脊椎动物Y染色体的进化和性别决定过程提供了一个机会。
