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Cell autonomous sex identity arises from the intrinsic properties of individual cells, determined by genetic and epigenetic factors encoded by their sex chromosomes. Unlike hormone-driven sex differentiation, where external chemical signals guide the development of sexual traits, CASI relies on the direct expression of genes and regulatory ...
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 ...
Offspring have two sex chromosomes: an offspring with two X chromosomes (XX) will develop female characteristics, and an offspring with an X and a Y chromosome (XY) will develop male characteristics, except in various exceptions such as individuals with Swyer syndrome, that have XY chromosomes and a female phenotype, and de la Chapelle Syndrome ...
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]
During meiosis, 5 of X form one chain, and 5 of Y form another chain. Thus, they behave effectively as a typical XY chromosomal system, except each of X and Y is broken into 5 parts, with the effect that recombinations occur very frequently at 4 particular points. [ 17 ]
[8] [40] During development, the volume of the SCN and the cell counts reach peak value at approximately 13 to 16 months after birth; at this age, the SCN contains the same number of cells as was found in adult male homosexuals, yet in a reference group of heterosexual males the cell numbers begin to decline to the adult value of 35% of the ...
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 ...
In human cells with more than one X chromosome, two long non-coding RNAs are produced: Tsix is produced by one X chromosome, and Xist is produced by all of the other X chromosomes. Tsix is a long non-coding RNA that prevents repression of an X chromosome, while Xist is a long non-coding RNA that acts to repress and condense an entire X chromosome.