Pioneering Oak Ridge scientist Liane “Lee” Branch Russell died at age 95, according to Tennessee Citizens for Wilderness planning, an organization Russell helped found and remained involved in until her death.

During her time at the Oak Ridge National Laboratory, the Austrian-born scientist discovered that the Y chromosome determines the male biological sex. Russell and her husband also created ORNL’s mouse laboratory, where she studied radiation biology and its effects on embryos.

Her groundbreaking work is the reason doctors now ask women if they are pregnant before conducting an X-ray.

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