XO

XO,

the designation of a cell in which or individual in whom only one sex chromosome is present. Either the other X or the Y chromosome is missing so that each cell is monosomic and contains a total of 45 chromosomes. All XO individuals are females with Turner's syndrome. Individuals with only a Y chromosome do not survive.

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XO

symbol for the karyotype in which there is only one sex chromosome, an X chromosome.

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XO genotype

in horses, pigs and cats causes infertile, usually anestrous, females; the uterus and external genitalia may be small and undeveloped.

XO ovarian dysgenesis

the second female X chromosome is missing, hence the XO of the title, and the animal, most commonly a mare, has small inactive ovaries which lack germ cells, and small uteri and external genitalia.