Mice can be male without Y chromosome | Science News

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Mice can be male without Y chromosome

Genetic manipulations enable female embryo to develop as opposite sex, study shows

2:00pm, January 28, 2016

MADE MALE  This male mouse (white) has no Y chromosome, but was able to father pups (brown) when scientists injected his immature sperm into eggs. Researchers made the mouse male by manipulating genes on other chromosomes. 

Researchers have created male mice with no trace of a Y chromosome, supposedly the defining hallmark of being male.

Reproductive biologist Monika Ward of the University of Hawaii in Honolulu and colleagues started with mice that have only one X chromosome (and no second sex chromosome). Normally those animals would develop as females. But when the researchers manipulated genes found on the X and another chromosome, the mice became males that could produce immature sperm. Those engineered males fathered offspring with reproductive assistance from the researchers, who injected the immature sperm into eggs, Ward and colleagues report in the Jan. 29 Science.

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