COLLABORATIVE RESEARCH: Sex Chromosome Evolution in Turtles

在大多数动物中，性别是由遗传构成（GSD）决定的，例如人类的性染色体对XX或XY，鸟类的性染色体对ZZ或ZW。然而，在某些其他动物中，性别是由环境温度（TSD）决定的。然而，在海龟物种中，可以找到这两种性别决定的例子。然而，不同性别决定机制存在的方式和原因尚不清楚。该合作项目将利用XX/XY、ZZ/ZW或TSD机制来比较海龟的染色体和性别相关基因，从而填补这一空白。特别是，本研究将测试(1)海龟的所有性染色体是否来自于一个共同的祖先对非性染色体（或“常染色体”），以及(2)海龟性染色体上的基因的分子进化是否与没有性染色体的TSD海龟的相同基因不同-即，位于性染色体上的基因序列在进化过程中是否与位于常染色体上的相同基因序列发生了不同的变化。本项目将把本科生基于发现的学习纳入本项目的实地和实验室模块，并将通过为学生及其导师提供直接培训机会，通过外展活动吸引妇女和少数民族，以及为研究人员提供进一步的机会，使他们成为少数民族的榜样，从而扩大代表性不足的群体对生物学的参与。

Sex is determined by genetic constitution (GSD) in most animals, such as by the sex chromosome pairs XX or XY in humans, or ZZ or ZW in birds. In certain other animals, however, sex is determined by environmental temperature (TSD). Among turtle species, however, examples of both types of sex determination can be found. It remains unclear, however, how and why different sex determining mechanisms exist. This collaborative project will help fill this gap by comparing the chromosomes and sex-related genes of turtles using XX/XY, ZZ/ZW, or TSD mechanisms for sex determination. Particularly, this research will test whether (1) all sex chromosomes in turtles derive from a common ancestral pair of non-sex chromosomes (or "autosomes"), and whether (2) the molecular evolution of genes located on turtle sex chromosomes differs from that of the same genes in TSD turtles, in which there are no sex chromosomes- i.e., whether the sequences of genes located on sex chromosomes change differently over evolutionary time than do the sequences of the same genes when they are located on autosomes. This project will integrate undergraduate discovery-based learning for undergraduates into the field and lab modules of this project and will broaden the participation of underrepresented groups in biology by providing direct training opportunities for students and their mentors, by engaging women and minorities through outreach activities, and by providing further opportunities for both the investigators to serve as role models for minorities.