Spotila J R, Spotila L D, Kaufer N F
Department of Bioscience and Biotechnology, Drexel University, Philadelphia, 19104.
J Exp Zool. 1994 Sep 15;270(1):117-27. doi: 10.1002/jez.1402700113.
Significant progress has been made in understanding mechanisms of genetic sex determination. The ZFY gene encodes a zinc finger protein but is not the primary signal in sex determination. The SRY gene is the testis determining gene in man, mouse, rabbit, and probably marsupial mouse and wallaby. Temperature dependent sex determination probably involves a modification of development of the indifferent gonad due to differential expression of one or more specific DNA sequences whose behavior is controlled by some temperature sensitive process or to differential action of a gene product such as a protein. There are ZFY and SRY-like genes in reptiles. We cloned and sequenced a portion of the ZFY gene (Zft) from snapping turtle (Chelydra serpentina) that is found in both sexes. We cloned and sequenced portions of SRY-like genes (Sra for SRY-related-autosomal) from snapping turtle. Similar genes are found in alligator (Alligator mississippiensis) and lizards. Cladistic analysis suggests that there are two or three major families of SRY-like genes in vertebrates in addition to sex specific SRY genes located on the Y chromosome of eutherian and marsupial mammals. When placed on a phylogenetic tree these data indicate that Sras were present in early tetrapods. Sequestering of the SRY gene on the Y chromosome probably happened only once and this may have been the defining moment that set the mammalian line of Therapsid reptiles apart from other reptilian groups.
在理解遗传性别的决定机制方面已经取得了重大进展。ZFY基因编码一种锌指蛋白，但不是性别决定的主要信号。SRY基因是人类、小鼠、兔子以及可能的有袋小鼠和沙袋鼠的睾丸决定基因。温度依赖性性别决定可能涉及由于一个或多个特定DNA序列的差异表达而导致的未分化性腺发育的改变，这些序列的行为受某些温度敏感过程控制，或者涉及基因产物（如蛋白质）的差异作用。爬行动物中有ZFY和SRY样基因。我们从两性都有的鳄龟（Chelydra serpentina）中克隆并测序了ZFY基因（Zft）的一部分。我们从鳄龟中克隆并测序了SRY样基因（与SRY相关的常染色体基因，简称Sra）的部分序列。在短吻鳄（Alligator mississippiensis）和蜥蜴中也发现了类似的基因。分支系统学分析表明，除了真兽类和有袋类哺乳动物Y染色体上的性别特异性SRY基因外，脊椎动物中还有两到三个主要的SRY样基因家族。当将这些数据置于系统发育树上时，表明Sras存在于早期四足动物中。SRY基因在Y染色体上的隔离可能只发生过一次，这可能是将兽孔目爬行动物的哺乳动物谱系与其他爬行动物群体区分开来的决定性时刻。
