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While cell autonomous sex identity emphasizes the intrinsic sex-specific properties of individual cells, the interplay between CASI and hormonal influences plays a critical role in shaping an organism's overall sexual phenotype. CASI and hormones are not mutually exclusive but instead represent complementary mechanisms of sexual differentiation.
The optimality hypothesis states too much variability in the MHC can result in a failure of T-cells to distinguish themselves non-selves, and thereby increase the risk of autoimmune disease. This would confer greater fitness to individuals without a large degree MHC diversity. [6] [13] Autoimmune diseases are associated with MHC loci. In humans ...
The Organizational-Activational Hypothesis states that steroid hormones permanently organize the nervous system during early development, which is reflected in adult male or female typical behaviors. [1] In adulthood, the same steroid hormones activate, modulate, and inhibit these behaviors. [2]
Figure One: The mesonephric System Pathway [7] Differentiation between the sexes of the sex organs occurs throughout embryological, fetal and later life. In both males and females, the sex organs consist of two structures: the internal genitalia and the external genitalia. In males, the gonads are the testicles and in females, they are the ovaries.
In humans, barring intersex conditions causing aneuploidy and other unusual states, it is the male that is heterogametic, with XY sex chromosomes.. Haldane's rule is an observation about the early stage of speciation, formulated in 1922 by the British evolutionary biologist J. B. S. Haldane, that states that if — in a species hybrid — only one sex is inviable or sterile, that sex is more ...
In contrast to asexual reproduction, sexual reproduction involves two parents. Both the parents produce gametes through meiosis, a special type of cell division that reduces the chromosome number by half. [3] During an early stage of meiosis, before the chromosomes are separated in the two daughter cells, the chromosomes undergo genetic ...
The hormonal theory of sexuality holds that, just as exposure to certain hormones plays a role in fetal sex differentiation, such exposure also influences the sexual orientation that emerges later in the individual. Prenatal hormones may be seen as the primary determinant of adult sexual orientation, or a co-factor.
Character state identity is the hypothesis that the particular condition in two or more taxa is "the same" as far as our character coding scheme is concerned. Thus, two Adenines at the same aligned nucleotide site are hypothesized to be homologous unless that hypothesis is subsequently contradicted by other evidence.