12th edition of my human genetics textbook


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Glenn Nichols, surrounded by his hospice team. The author is in yellow.

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Genetic Linkage

A Common Ancestry Metric Is Based On a Century-Old Discovery by a 19-Year-Old: CentiMorgans Explained

December 2, 2018

Tags: Ancestry.com, Sturtevant, centiMorgan

Iíve been immersed in genetic genealogy, following up on a recent contact from a relative I didnít know existed. While trying to imagine scenarios that might explain how we came to be connected, I contacted Ancestry.com for assistance in seeing actual data. When I found the obvious drop-down menus next to my matches on the website, I was astounded to recognize the unit used to assess the closeness of relationships Ė a centiMorgan.

Iím sure thatís Greek to most people. But to a former Drosophila (fruit fly) geneticist like me, ďcentiMorganĒ (cM) brought an instant meaning: distance along a chromosome.

Invention of the centiMorgan is one of my favorite tales from the history of genetics. It provided the very first genetic map, and inspired the variations on the theme that were to come, including full genome sequencing.

The intuition that has sent millions of people googling centiMorgans, with more to come after all those DNA kits are opened and spat into for Christmas, goes back to a sleep-deprived 19-year-old with a fantastically brilliant idea, 105 years ago.

To continue reading go to DNA Science, my blog for Public Library of Science, where this article first appeared.

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