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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.
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 ...
Sexual selection is a biological way one sex chooses a mate for the best reproductive success. Most compete with others of the same sex for the best mate to contribute their genome for future generations. This has shaped human evolution for many years, but reasons why humans choose their mates are not fully understood.
Autocrine signaling is a form of cell signaling in which a cell secretes a hormone or chemical messenger (called the autocrine agent) that binds to autocrine receptors on that same cell, leading to changes in the cell. [1] This can be contrasted with paracrine signaling, intracrine signaling, or classical endocrine signaling.
The distinct hormone profiles characterizing each phase represent two stable states, with sharp transitions between them ensuring proper timing of ovulation and endometrial preparation. As previously stated, during the follicular phase, estrogen and LH levels rise, and entry into the luteal phase does not occur unless a surge in these hormones ...
The Lyon hypothesis states that in cells with multiple X chromosomes, all but one are inactivated early in embryonic development in mammals. [ 3 ] [ 4 ] The X chromosomes that become inactivated are chosen randomly, except in marsupials and in some extra-embryonic tissues of some placental mammals, in which the X chromosome from the sperm is ...
The thrifty gene hypothesis, or Gianfranco's hypothesis [citation needed] is an attempt by geneticist James V. Neel to explain why certain populations and subpopulations in the modern day are prone to diabetes mellitus type 2. He proposed the hypothesis in 1962 to resolve a fundamental problem: diabetes is clearly a very harmful medical ...