In her memoir for her husband she wrote that he was a man of amazing courage and mental vitality enabling him to gain a career in biochemistry despite his physical circumstances, and with her encouragement and assistance.

[6][2] In 1903, she joined William Bateson's genetics group at Cambridge where she began her study focusing on the inheritance of petal colour in Antirrhinum (snapdragons).

Bateson was the English biologist who was the first person to use the term genetics to describe the study of heredity, and the chief populariser of the ideas of Gregor Mendel following their rediscovery in 1900.

Bateson and Onslow, alongside a research group mainly made up of Newnham College graduates, carried out a series of breeding experiments in various plant and animal species between 1903 and 1910.

In 1907, Wheldale published a full explanation what became termed epistasis, the phenomenon of dominant-like relationship between different pairs of nonallelomorphic factors.

[11] She joined the biochemistry lab of Frederick Gowland Hopkins at Cambridge University in 1914, where she pursued the biochemical aspects of petal colour, whose genetics she had elucidated during her work with Bateson.

[10] In combining genetics and biochemistry she became one of the first biochemical geneticists and paved the way for the later successes of such seminal investigators as Edward Tatum and George Beadle.

[2] In 2010 the Royal Institution of Great Britain staged a play, entitled Blooming Snapdragons, about four early-20th-century women biochemists, one of whom was Onslow.

Written by Liz Rothschild and directed by Sue Mayo, it had been commissioned by the John Innes Centre where Onslow worked.