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Sexual differentiation is the process of development of the sex differences between males and females from an undifferentiated zygote. [1] [2] Sex determination is often distinct from sex differentiation; sex determination is the designation for the development stage towards either male or female, while sex differentiation is the pathway towards the development of the phenotype.
Male development can only occur when the fetal testis secretes key hormones at a critical period in early gestation. The testes begin to secrete three hormones that influence the male internal and external genitalia: they secrete anti-Müllerian hormone (AMH), testosterone, and dihydrotestosterone (DHT). Anti-Müllerian hormone causes the ...
The human brain. Differences in male and female brain size are relative to body size. [83] Early research into the differences between male and female brains showed that male brains are, on average, larger than female brains. This research was frequently cited to support the assertion that women are less intelligent than men.
This is an accepted version of this page This is the latest accepted revision, reviewed on 29 January 2025. Process in which chromosomes are replicated and separated into two new identical nuclei For the type of cell division in sexually reproducing organisms used to produce gametes, see Meiosis. For excessive constriction of the pupils, see Miosis. For the parasitic infestation, see Myiasis ...
The Y chromosome is one of two sex chromosomes in therian mammals and other organisms.Along with the X chromosome, it is part of the XY sex-determination system, in which the Y is the sex-determining chromosome because the presence of the Y chromosome causes offspring produced in sexual reproduction to be of male sex.
A gynandromorph can have bilateral symmetry—one side female and one side male. [24] Alternatively, the distribution of male and female tissue can be more haphazard. Bilateral gynandromorphy arises very early in development, typically when the organism has between 8 and 64 cells. [25] Later stages produce a more random pattern. [citation needed]
Maternal influences may also be possible that affect sex determination in such a way as to produce fraternal twins equally weighted between one male and one female. [28] The time at which insemination occurs during the estrus cycle has been found to affect the sex ratio of the offspring of humans, cattle, hamsters, and other mammals. [25]
Anisogamy is a core element of sexual dimorphism that helps to explain phenotypic differences between sexes. [16] [17] Researchers estimate that over 99.99% of eukaryotes reproduce sexually. [18] Most do so by way of male and female sexes, both of which are optimized for reproductive potential.