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The Modern Papers · MP·08 · 1990

1990: Reading the polar body

In Chicago, Verlinsky's team tested the chromosomes an egg sets aside, to learn which copy of a gene the egg had kept.

The story

As an egg matures it sets aside a small packet of chromosomes, the first polar body. Yury Verlinsky's team at Illinois Masonic Medical Center reasoned that if a mother carried one faulty copy of a gene, testing the polar body would show which copy the egg had kept.

For a couple at risk of alpha-1-antitrypsin deficiency, they removed the polar bodies from seven eggs and tested them by PCR. Two embryos from eggs that held the unaffected gene were transferred. No pregnancy followed, but removing the polar body had not harmed fertilisation or growth to the blastocyst stage.

The same year Alan Handyside's team in London reported pregnancies after testing a cell from the embryo itself (FP·11). Between them, the two papers opened genetic testing in IVF.

“genetic analysis of the first polar body allows the identification of oocytes that contain the maternal unaffected gene.”From the paper's abstract

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