Two prevailing paradigms explain the diversity of sex-determining modes in reptiles. Many researchers, particularly those who study reptiles, consider genetic and environmental sex-determining mechanisms to be fundamentally different, and that one can be demonstrated experimentally to the exclusion of the other. Other researchers, principally those who take a broader taxonomic perspective, argu...

Many animal taxa show frequent and rapid transitions between male heterogamety (XY) and female heterogamety (ZW). We develop a model showing how these transitions can be driven by sex-antagonistic selection. Sex-antagonistic selection acting on loci linked to a new sex-determination mutation can cause it to invade, but when acting on loci linked to the ancestral sex-determination gene will inhi...

those produced by x-irradiation, the above result and further experiments producing mutations with neutrons may lead to new conclusions regarding the interaction of radiation ions with genes and hence of the size and structure of the gene. It is interesting to note that the ratio of effectiveness (5 or 6 to 1) for the effects on mature sperm of neutron as compared with x-irradiation is comparab...

The isolation and analysis of Drosophila mutants with altered sexual orientation lead to the identification of novel branches in the sex-determination cascade which govern the sexually dimorphic development of the nervous system. One such example is the fruitless (fru) gene, the mutation of which induces male-to-male courtship and malformation of a male-specific muscle, the muscle of Lawrence (...

It was a population based cross sectional study done with the objective of comparing some parameters (attitude & practice) of gender discrimination (GD) in rural and urban areas of Ahmedabad district. A population of 963 (446 urban & 517 rural) showed alarmingly adverse sex ratio (SR) as low as 562 among urban preschoolers. GD was prevalent in both study areas but manifested differently. Prefer...

Sex is determined in Drosophila by the activity of the Sex-lethal master regulator. Activity of Sex-lethal is initiated early in females by chromosome-counting transcription factors, then reinforced by signaling through the Janus kinase pathway.

The morphological characteristics of the humeral bone has been investigated in recent times with studies showing varying degrees of sexual dimorphism. Osteologists and forensic scientists have shown that sex determination methods based on skeletal measurements are population specific, and these population-specific variations are present in many body dimensions. The present study aims to establi...

The effect of linkage and epistasis on the evolution of the sex-ratio is studied in a symmetric two-locus model of autosomal sex determination closely related to the symmetric viability model of R. C. Lewontin and K. Kojima. R. A. Fisher's expectation of an even sex ratio for autosomal sex determination by a single gene governs the dynamics when the loci are tightly linked. However, recombinati...

Sex determination in honeybees involves a multi-allelic locus, such that homozygotes develop as males and heterozygotes as females. In this issue of Cell, report the cloning of the sex-determining gene, csd. It codes for an SR protein, and different alleles have very different amino-acid sequences. Inactivating csd leads to development as a male.

BACKGROUND Investigating gonadal gene expression is important in attempting to elucidate the molecular mechanism of sex determination and differentiation in the model species zebrafish. However, the small size of juvenile zebrafish and correspondingly their gonads complicates this type of investigation. Furthermore, the lack of a genetic sex marker in juvenile zebrafish prevents pooling gonads ...