Mice Become Male Without Male Chromosome

Y Chromosome is Gone!
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Scientists have created generations of mice that don’t need a Y Chromosome and many of which are able to sire viable offspring themselves.

In 2013, researcher Monika Ward and colleagues of the University of Hawaii in Honolulu, showed that only a miniscule amount of Y chromosome information was needed to produce a viable male that could father a litter. Now, Dr. Ward and team have discovered a way to manipulate the X chromosome of the male and an autosomal chromosome (non-sex chromosome) to produce males that can produce viable sperm without ever having a Y chromosome at all.

2 year old mouse with no Y chromosome

2 year old mouse with no Y chromosome – Image Source: Amanda Shell via Science


As the team discovered that only a few genes were necessary for male formation, they removed those genes from the Y chromosome and implanted them in the X chromosome. Then, they amplified the expression of similar genes on the X chromosome and an additional chromosome. Once they successfully implanted the modified sperm into a female egg, a generation of mice were born with no Y chromosome. Generations later, males were found to still be able to produce viable offspring albeit with some assistance.

As a result of this experiment, researchers believe that the X chromosome in some way has a type of built in redundancy to continue the species even if something were to go wrong with the Y chromosome. Future studies may be able to further reproductive technologies in humans.


Cover Image: Yasuhiro Yamauchi

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