Lizards Chromosome

Transcriptome and genome assemblies of four Australian reptile species. A The pipeline of identifying sex-linked transcripts of river turtle, worm lizard and marbled gecko using transcriptomes of sexed tissues, and amplified probes from the microdissected sex chromosomes. The probes have been validated by chromosome painting, and Illumina reads generated from the probes were used to identify

Lizards represent unique model organisms in the study of sex determination and sex chromosome evolution. Among tetrapods, they are characterized by an unparalleled diversity of sex determination systems, including temperature-dependent sex determination TSD and genetic sex determination GSD under either male or female heterogamety.

Proposed model for lizard sex chromosome evolution, modified from . Many Reptiles are likely to have followed the currently held view of sex chromosome evolution as proposed for vertebrates but may also involve other regulatory molecular mechanisms e.g., epigenetic. The sex determination sensu sex chromosomes in genotypic sex determination

The lizards are all female and parthenogenetic, meaning their eggs develop into embryos without fertilization. But before the eggs form, Baumann's team discovered, the females' cells gain twice the usual number of chromosomes during meiosis. This results in a standard pair of chromosones derived from two sets of pairs.

The new research by Baumann and his team reveal that these lizards maintain genetic richness by starting the reproductive process with twice the number of chromosomes as their sexually reproducing

This implies that there have been multiple transitions between TSD and GSD, and between XY and ZW sex chromosome systems. Approximately 1,000 species of lizards have been karyotyped and among those, fewer than 200 species have sex chromosomes, yet they display remarkable diversity in morphology and degree of degeneration.

Lizards represent unique model organisms in the study of sex determination and sex chromosome evolution. Among tetrapods, they are characterized by an unparalleled diversity of sex determination

Pathways of sex chromosome diversification in lizards A diversification by progressive heterochromatinization, B diversification by chromosome inversion and C formation of multiple sex chromosome systems by sex chromosome-autosome fusion.Repeated sequences are known to play a significant role in sex chromosome evolution and their preferential accumulation on the heteromorphic

Identification of the linkage group of the Z sex chromosomes of the sand lizard Lacerta agilis, Lacertidae and elucidation of karyotype evolution in lacertid lizards. Chromosoma 123 563-575.

This implies that there have been multiple transitions between TSD and GSD, and between XY and ZW sex chromosome systems. Approximately 1,000 species of lizards have been karyotyped and among those, fewer than 200 species have sex chromosomes, yet they display remarkable diversity in morphology and degree of degeneration.