Singh L, Purdom I F, Jones K W
Chromosoma. 1976 Dec 6;59(1):43-62. doi: 10.1007/BF00327708.
The satellite DNA (SATELLITE III) which is mainly represented in the female of Elaphe radiata (Ophidia, Colubridae) has been isolated and its buoyant density has been determined (delta equals 1.700 g cm-3). In situ hybridisation of radioactive complementary RNA of this satellite DNA with the chromosomes of different species has revealed that it is mainly concentrated on the W sex chromosome and its sequences are conserved throughout the sub-order Ophidia. From hybridisation studies these sequences are absent from the primitive family Boidae which represents a primitive state of differentiation of sex chromosomes. Chromosome analysis and C-banding have also revealed the absence of heteromorphism and of an entirely heterochromatic chromosome in the species belonging to the primitive family and their presence in the species of highly evolved families. It is suggested that the origin of satellite DNA (satellite III) in the W chromosome is the first step in differentiation of W from the Z in snakes by generating asynchrony in the DNA replication pattern of Z and W chromosomes and thus conceivably reducing the frequency of crossing-over between them which is the prerequisite of differentiation of sex chromosomes. Presence of similar sex chromosome associated satellite DNA in domestic chicken suggests its existence in a wider range of vertebrates than just the snakes.
已分离出主要存在于红点锦蛇（游蛇科，蛇亚目）雌性个体中的卫星DNA（卫星III），并测定了其浮力密度（δ = 1.700 g/cm³）。该卫星DNA的放射性互补RNA与不同物种的染色体进行原位杂交显示，它主要集中在W性染色体上，其序列在整个蛇亚目内保守。杂交研究表明，在代表性染色体分化原始状态的原始蟒科中不存在这些序列。染色体分析和C带分析还显示，原始科的物种中不存在异形性和完全异染色质的染色体，而在高度进化科的物种中存在。有人提出，W染色体中卫星DNA（卫星III）的起源是蛇类中W染色体从Z染色体分化的第一步，通过在Z和W染色体的DNA复制模式中产生异步性，从而可以想象降低它们之间的交叉频率，这是性染色体分化的前提。家鸡中存在类似的与性染色体相关的卫星DNA，表明其存在于比蛇类更广泛的脊椎动物中。
