In 1958, French paediatrician Marthe Gautier helped produce the laboratory evidence linking Down's syndrome to an extra chromosome at the Armand-Trousseau children's hospital in Paris.

Her contribution became the subject of a long-running dispute after Jérôme Lejeune emerged as the best-known figure associated with the discovery, while a 2014 assessment by France's medical research institute stressed Gautier and department head Raymond Turpin's indispensable roles.

In 1956, researchers established that human cells normally contain 46 chromosomes, prompting Turpin to investigate a chromosomal cause for Down's syndrome.

Gautier had learned cell-culture techniques during a scholarship at Harvard in 1955 and brought that expertise back to Paris.

Gautier developed a method for growing cells from children with the condition, using rooster plasma and her own blood serum.

The preparations made it possible to examine chromosomes, although the laboratory lacked equipment to photograph the smallest structures clearly.

Who first counted 47 chromosomes remains contested. Gautier's 2009 account described her role in preparing and examining the cells, while Lejeune's laboratory notebook, cited by his foundation, records a 47-chromosome observation in a child with Down's syndrome on 22 May 1958. A second entry on 13 June referred to a different condition.

The foundation also points to a letter Turpin sent Lejeune on 27 October 1958, saying Gautier and another researcher, Mrs Massé, were still obtaining counts of 46.

Although the notebook evidence challenges the claim that Gautier alone made the first count, it does not diminish her role in developing the cell-culture method.

Lejeune presented the finding at McGill University in 1958, before the research was published in January 1959, listing him first, Gautier second and Turpin last, with Gautier's surname misspelled as 'Gauthier'; a second communication followed in March.