P9-11 Sat Jan 2 Dosage balance of the crested gecko (Correlophus ciliatus) ZZ/ZW sex chromosomes Keating, SE*; Pinto, B; Gamble, T; Marquette University; Marquette University; Marquette University skeating63@gmail.com
Sex chromosomes evolve from an ancestral chromosome pair that acquires a sex-determining locus. The sex-determining locus will become linked to a sexually antagonistic allele through recombination suppression, preventing the proto-sex chromosomes from repairing DNA and allow mutations to accumulate. Over time, the sex-limited chromosome (W chromosome in ZZ/ZW systems) will begin to degenerate and lose genes, leaving Z-linked genes hemizygous in the heterogametic sex (females). If the halved gene dose lowers average female expression levels, dosage balance will be lost as males and females will no longer have equal average expression levels on the sex chromosomes. However, there is a dearth of studies on the presence or absence of dosage balance in certain organisms, such as squamates lizards, and more work is needed to understand whether gene expression must be balanced between the sexes. Here, I use RNAseq data to examine dosage balance on the Z chromosome of the crested gecko, Correlophus ciliatus. I examine the female:male expression ratio of autosomal and sex-linked genes and show that female and male expression is equal except for hemizygous Z-linked gene, in which the W gametolog is no longer expressed. Thus, when genes are lost from the W chromosome, Z-linked genes do not appear to be upregulated in females relative to males. This demonstration of the lack of dosage balance within a gecko species contributes to our growing knowledge on sex chromosome degeneration and gene loss.