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A safe way to separate male from female-producing sperm has been discovered
by Ian Cumming of the University of Bristol (GB 2 360 360). He says today’s
cell-sorting methods risk genetic damage by using fluorescent dyes to make the
larger sperm, which contain an X chromosome, look brighter than smaller
Y-bearing cells. Instead, he proposes that sperm are washed in chicken egg yolk
to expose the proteins on their surface membrane. The cells are then put in a
buffer solution and run past electrodes carrying 900 volts. A slight—and
not fully understood—natural difference in surface charging draws the X
chromosome bearers towards the electrodes, while the Y cells pass straight
through.