COLLABORATIVE RESEARCH: Sex Chromosome Evolution in Turtles

在大多数动物中，性别由遗传构成(GSD)决定，例如人类的性别染色体对XX或XY，鸟类的性别染色体对ZZ或ZW。然而，在某些其他动物中，性别由环境温度(TSD)决定。然而，在海龟物种中，这两种性别决定的例子都可以找到。然而，目前还不清楚不同的性别决定机制是如何存在的，以及为什么存在。这个合作项目将通过使用XX/XY、ZZ/ZW或TSD性别决定机制比较海龟的染色体和性别相关基因来帮助填补这一空白。具体地说，这项研究将测试(1)海龟的所有性染色体是否来自一对共同的祖先非性别染色体(或常染色体)，以及(2)位于龟性染色体上的基因的分子进化是否与TSD海龟中没有性染色体的相同基因的分子进化不同--即，位于性染色体上的基因序列是否会随着进化时间的推移而发生不同于位于常染色体上的相同基因序列的变化。该项目将把本科生以发现为基础的学习纳入该项目的实地和实验室单元，并将通过为学生及其导师提供直接培训机会、通过外联活动吸引妇女和少数群体参与以及为这两名研究人员提供更多机会为少数群体树立榜样，扩大生物领域代表性不足群体的参与。

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.