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Abstract
The accurate and timely initiation of sex determination is fundamental tospecies survival and reproductive success. Despite its importance, genetic sex
determination mechanisms have only been carefully studied in a few vertebrate
species, and our understanding of reptilian genetic sex determination systems
remains limited. With over 12,000 species, reptiles make up one of the largest
vertebrate species groups and, unlike typical model systems such as mammals
and birds, a highly diverse array of sex determination systems have been
observed. Most of what we know about genetic sex determination comes from
groups that have very little diversity in the underlying genetic mechanisms of sex
determination, i.e., we know a lot about a little. By examining the molecular
mechanisms underlying genetic sex determination in more diverse species
groups, we can gain a broader and deeper understanding of genetic sex
determination across the tree of life. Here, I explore the ancient, deeply
conserved XX/XY genetic sex determination system of Anolis, with a particular
focus in uncovering the genetic signal cascade, clarifying the timing of embryonic
gonad differentiation, tracing the evolution of the sex chromosomes, identifying
the genetic basis of primary sex determination, and examining dosage
compensation in the brown anole lizard, Anolis sagrei. Using genomic and
transcriptomic methods, I propose rpl6y as a candidate determinant of primary
sex determination in A. sagrei. Additionally, I demonstrate regional differences in
dosage compensation across the A. sagrei X chromosome. This work reveals a
novel mechanism for genetic sex determination in Anolis and the nuances of
dosage compensation in neo-sex chromosome systems that have undergone
fusion events. This work is the beginning of large-scale comparative work across
pleurodonts, the order to which Anolis lizards belong.