US makes history with first all-female spacewalk

US astronauts Christina Koch and Jessica Meir on Friday became the first all-female pairing to carry out a spacewalk—a historic milestone as NASA prepares to send the first woman to the Moon.

Male and female mice have different brain cells

Caltech researchers have discovered rare brain cell types that are unique to male mice and other types that are unique to female mice. These sex-specific cells were found in a region of the brain that governs both aggression ...

How status sticks to genes

Those at the bottom of the social ladder are known to live shorter and sicker lives than those at the top. And the stress of life at the bottom may have long-term health effects that even upward mobility can't undo, according ...

Breakthrough in sex-chromosome regulation

Researchers at Karolinska Institutet in Sweden have uncovered a chromosome-wide mechanism that keeps the gene expression of sex chromosomes in balance in our cells. The findings shed light on molecular reasons for early miscarriage ...

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Female

Female (♀) is the sex of an organism, or a part of an organism, which produces mobile ova (egg cells). The ova are defined as the larger gametes in a heterogamous reproduction system, while the smaller, usually motile gamete, the spermatozoon, is produced by the male. A female individual cannot reproduce sexually without access to the gametes of a male (an exception is parthenogenesis). Some organisms can reproduce both sexually and asexually.

There is no single genetic mechanism behind sex differences in different species and the existence of two sexes seems to have evolved multiple times independently in different evolutionary lineages. Other than the defining difference in the type of gamete produced, differences between males and females in one lineage cannot always be predicted by differences in another. The concept is not limited to animals; egg cells are produced by chytrids, diatoms, water moulds and land plants, among others. In land plants, female and male designate not only the egg- and sperm-producing organisms and structures, but also the structures of the sporophytes that give rise to male and female plants.

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