in previous years, identification of fetal cells in maternal blood circulation has caused a new revolution in non-invasive method of prenatal diagnosis. low number of fetal cells in maternal blood and long-term survival after pregnancy limited the use of fetal cells in diagnostic and clinical applications. with the discovery of cell-free fetal dna (cffdna) in plasma of pregnant women, access to...

Sex in reptiles is determined by genes on sex chromosomes or by incubation temperature. Previously these two modes were thought to be distinct, yet we show that high incubation temperatures reverse genotypic males (ZZ) to phenotypic females in a lizard with ZZ and ZW sex chromosomes. Thus, the W chromosome is not necessary for female differentiation. Sex determination is probably via a dosage-s...

BACKGROUND Many different environmental and genetic sex-determination mechanisms are found in nature. Closely related species can use different master sex-determination switches, suggesting that these developmental pathways can evolve very rapidly. Previous cytological studies suggest that recently diverged species of stickleback fish have different sex chromosome complements. Here, we investig...

introduction: the existence of sexual dimorphism in human skeletons especially skull and its medico-legal importance had long been studied [3] [2,1]. this study has investigated the existence of sexual dimorphism in cranial dimensions of nigerian population. methods: a total of 100 adult dry skulls, (78 males, 22 females) free from damage and deformity fully ossified from departments of anatomy...

The study of sex determination in model organisms has been especially fruitful in increasing our understanding of developmental biology, gene regulation and evolutionary mechanisms. The free living nematode, Caenorhabditis elegans, can develop as one of two sexes; male or self-fertilizing hermaphrodite. Here we discuss the progress toward a genetic and molecular understanding of that decision. ...

Sex determination or the commitment of the embryo to its sexual fate is a fundamental developmental process with paramount consequences in ecology and evolution. This process, whether triggered by environmental factors or genotypic constitution, can be derailed by environmental contaminants that alter the endocrine system, which is a key component of the regulatory network underlying vertebrate...

Genomic structure affects the expression and evolution of phenotypes via its effect on genomic function. One example is the presence of sex chromosomes and the development of the sexual phenotype. Multiple forces account for the evolution of genomic structure and function, some acting synergistically and some in an antagonistic manner, in a co-evolutionary process between genomic architecture a...

Although much progress has been achieved in understanding the genetic basis of adaptation, the drivers of genome evolution remain obscure. For instance, extensive variation among reptilian genomes continues largely unexplained, yet reptiles hold critical clues about vertebrate evolution. Turtles posses diverse chromosome numbers (2N = 28-66) derived from extensive genomic rearrangements, plus v...

Somatic and germline sex determination pathways have diverged significantly in animals, making comparisons between taxa difficult. To overcome this difficulty, we compared the genes in the germline sex determination pathways of Caenorhabditis elegans and C. briggsae, two Caenorhabditis species with similar reproductive systems and sequenced genomes. We demonstrate that C. briggsae has orthologs...

The diversity and patchy phylogenetic distribution of genetic sex-determining mechanisms observed in some taxa is thought to have arisen by the addition, modification, or replacement of regulators at the upstream end of the sex-determining pathway. Here, I review the various evolutionary forces acting on upstream regulators of sexual development that can cause transitions between sex-determinin...