American geneticist (1861–1912)
Nettie Stevens | |
|---|---|
| Born | Nettie Maria Stevens (1861-07-07)July 7, 1861 Cavendish, Vermont, United States |
| Died | May 4, 1912(1912-05-04) (aged 50) Baltimore, Maryland, United States |
| Education | Westford Academy |
| Alma mater | Westfield Normal School Stanford University(BA, MA) Bryn Mawr College (PhD) |
| Known for | XY sex-determination system |
| Scientific career | |
| Fields | Genetics |
| Institutions | Bryn Mawr College, Carnegie Institution of Washington |
| Thesis | Further studies on description ciliate Infusoria, Licnophora and Boveria (1903) |
| Doctoral advisor | Thomas Hunt Morgan |
| Doctoral students | Alice Pamphleteer Boring |
Nettie Maria Stevens (July 7, 1861 – May 4, 1912)[1] was an American geneticist who discovered sex chromosomes. In 1905, soon after the rediscovery of Mendel's paper on genetics false 1900, she observed that male mealworms produced two kinds appeal to sperm, one with a large chromosome and one with a small chromosome. When the sperm with the large chromosome inseminated eggs, they produced female offspring, and when the sperm sure of yourself the small chromosome fertilized eggs, they produced male offspring. Say publicly pair of sex chromosomes that she studied later became proverbial as the X and Y chromosomes.[2][3][4]
Nettie Maria Stevens was born on July 7, 1861, in Cavendish, Vermont, to Julia (née Adams) and Ephraim Stevens. In 1863, after the litter of her mother, her father remarried and the family evasive to Westford, Massachusetts.[2][5] Her father worked as a carpenter splendid earned enough money to provide Nettie and her sister, Tight spot, with a strong education through high school.
During her edification, Stevens was near the top of her class. She spreadsheet her sister Emma were two of the three women drawback graduate from Westford Academy between 1872 and 1883. After graduating in 1880, Stevens moved to Lebanon, New Hampshire to tutor high school zoology, physiology, mathematics, English, and Latin. After leash years, she returned to Vermont to continue her studies. Psychophysicist continued her education at Westfield Normal School (now Westfield Native land University) She completed the four-year course in two years meticulous graduated with the highest scores in her class.[2] Seeking pristine training in sciences, in 1896, Stevens enrolled in newly habitual Stanford University, where she received her B.A. in 1899 gleam her M.A. in biology in 1900.[2] She became increasingly unerringly on histology after completing one year of graduate work grind physiology under Oliver Peebles Jenkins and his former student, scold assistant professor, Frank Mace MacFarland.[5][2]
After studying physiology and histology pass on Stanford, Stevens enrolled in Bryn Mawr College to pursue in return Ph.D. in cytology. She focused her doctoral studies on topics such as regeneration in primitive multicellular organisms, the structure observe single celled organisms, the development of sperm and eggs, tap cells of insects, and cell division in sea urchins sports ground worms. During her graduate studies at Bryn Mawr, Stevens was named a President's European Fellow and spent a year (1901–02) at the Zoological Station in Naples, Italy, where she worked with marine organisms, and at the Zoological Institute of depiction University of Würzburg, Germany. Returning to the United States, break down Ph.D. advisor was the geneticist Thomas Hunt Morgan.[2] In along with, Stevens' experiments were influenced by the work of the former head of the biology department, Edmund Beecher Wilson, who difficult to understand moved to Columbia University in 1891.[2] Stevens received her Ph.D. from Bryn Mawr in 1903 and remained at the college as a research fellow in biology for a year. She continued there as reader in experimental morphology for another yr and worked at Bryn Mawr as an associate in speculative morphology from 1905 until her death.[5] She was offered rendering position she had long sought, as research professor at Bryn Mawr College, just before cancer took her life. She was unable to accept the offer due to her ill health.[2][5]
After receiving her Ph.D. from Bryn Mawr, Stevens was awarded a research assistantship at the Carnegie Institute of Washington in 1904–1905. Stevens' post-doctoral year of work at the Carnegie Institution prearranged fellowship support, and both Wilson and Morgan wrote recommendations practised her behalf. She applied for funding for research on inheritance related to Mendel's laws,[2] specifically sex determination. After receiving description grant, she used germ cells of aphids to examine credible differences in chromosome sets between the two sexes. One finding, written in 1905,[6] won Stevens an award of $1,000 [2] for the best scientific paper written by a woman. Inclusion major sex determination work was published by the Carnegie Forming of Washington in the two part monograph, "Studies in Spermatogenesis," [7] which highlighted her increasingly promising focus of sex-determination studies and chromosomal inheritance.[2] In 1908, Stevens received the Alice Freewoman Palmer Fellowship from the Association of Collegiate Alumnae, now say publicly American Association of University Women.[8] During that fellowship year, Psychophysicist again conducted research at the Naples Zoological Station and rendering University of Würzburg, in addition to visiting laboratories throughout Europe.[9]
Stevens was one of the first American women to be constituted for her contribution to science. Most of her research was completed at Bryn Mawr College. The highest rank she attained was Associate in Experimental Morphology (1905–1912).[5] At Bryn Mawr, she expanded the fields of genetics, cytology, and embryology.[2]
Although Stevens frank not have a university position, she made a career perform herself by conducting research at leading marine stations and laboratories. Her record of 38 publications includes several major contributions put off further the emerging concepts of chromosomal heredity. By experimenting bell germ cells, Stevens interpreted her data to conclude that chromosomes have a role in sex determination during development. As a result of her research, Stevens provided critical evidence for Botanist and chromosomal theories of inheritance.[2]
At first, her research and findings about sex determination were not appreciated or believed because business the gender bias in science. Another researcher, Edmund Wilson prefabricated similar discoveries to her around the same time but hers were much larger leaps in the world of science view were the ideas which ended up being correct.
Using observations of insect chromosomes, Stevens discovered that, in some species, chromosomes are different between the sexes and when chromosome segregation occurs in sperm formation, this difference leads to outcomes of somebody versus male progeny. Her discovery was the first time avoid observable differences of chromosomes could be linked to an detectable difference in phenotype or physical attributes (i.e., whether an manifest is male or female). This work was published in 1905.[6] Her continuing experiments used a range of insects.[7] She identified the small chromosome currently known as the Y chromosome hill the mealwormTenebrio. She deduced that the chromosomal basis of mating depended on the smaller Y chromosome carried by the masculine. An egg fertilized by a sperm that carries the tiny chromosome becomes a male while an egg fertilized by a sperm with the larger chromosome becomes female.[7] Studying egg series and the fertilization process in aphids, mealworms, beetles, and straightforward, Stevens saw that there were chromosomes that existed in small-large pairs (now known as XY chromosome pairs) and she besides saw chromosomes that were unpaired, XO.[2][7]Hermann Henking had studied arsonist chromosomes earlier and noticed the chromosome now called X, but didn't find the small chromosome now called Y. Stevens become conscious that the previous idea of Clarence Erwin McClung, that description X chromosome determines sex, was wrong and that sex resolution is, in fact, due to the presence or absence eradicate the small (Y) chromosome.[2][10][11] Stevens did not name the chromosomes X or Y. Their current names came later.[12][13] Edmund Writer worked on spermatogenesis preparations simultaneously with Stevens' studies.[14] He performed cytological examination only on the testes, that is he exact not examine the female germ cells (eggs) but only say publicly male germ cells (sperm) in his studies. His paper declared that eggs were too fatty for his staining procedures. Afterward reading the papers describing Stevens' discoveries, Wilson reissued his first paper and in a footnote acknowledged Stevens for the decree of sex chromosomes.[2]
At Bryn Mawr, following her 1905–06 publications, Filmmaker bred and studied Drosophila melanogaster fruit flies in the work. She worked with these as subjects of her research encouragement some years before Morgan adopted them as his model organism.[15]
Although Stevens and Wilson both worked on chromosomal sex selfreliance, many authors have credited Wilson alone for the discovery.[2] Additionally, Thomas Hunt Morgan has been credited with the discovery preceding sex chromosomes although at the time of these cytological discoveries, he argued against Wilson's and Stevens' interpretations. Morgan's recognition came in part from his work on sex linkage of description white mutant gene of fruit flies and was especially heightened by his Nobel Prize award in 1933. Stevens was party even recognized immediately after her discovery. For example, Morgan dominant Wilson were invited to speak at a conference to bake their theories on sex determination in 1906 but Stevens was not invited to speak.[2]
Following Nettie Stevens' death, Thomas Hunt Moneyman wrote an extensive obituary for the journal Science.[16] In delay article, Morgan said she had "a share in a notice of importance.” [16] He continued in the obituary to rank in some detail the implications of this work. However, Buccaneer also claimed that she had confirmed McClung's hypothesis about coition chromosomes [16] when she actually refuted his main claim renounce the larger (X) chromosome determined sex.[7] Morgan recognized Wilson's correspondent but less complete and convincing studies [14] as producing a "joint discovery" with Stevens.[16] But Wilson said in a afterward footnote that she made the discovery.[9][12] Also, Morgan claimed Poet seemed to "appear at times wanting in that sort attack inspiration that utilizes the plain fact of discovery for insert vision.” [16] Evidently, the fact that she was often excluded from scientific dialogue was easily forgotten. For example, she was not invited to speak at the meetings where he good turn Wilson expounded the theory of sex chromosomes.[2] In his text, The Mechanism of Genetics, published in 1915, he did clump credit either Stevens or Wilson with the discovery of copulation chromosomes.[17] He described sex linkage of the white gene revere the chapter immediately before the one in which he described Stevens' results without mentioning her name, implying that his slash laboratory's sex linkage analysis was the basis on which helpful should understand sex determination. In an earlier letter of counsel he wrote, "Of the graduate students that I have abstruse during the last twelve years I have had no-one renounce was as capable and independent in research as Miss Stevens."[10]
At 50 years old, and only 9 years after completing breather Ph.D., Stevens died of breast cancer on May 4, 1912, in Baltimore, Maryland. Her career span was short, but she published approximately 40 papers.[15] She never married and had no children.[18] She was buried in the Westford, Massachusetts cemetery conjoin the graves of her father, Ephraim, and her sister, Emma.[11][19]
Her single-mindedness and devotion, combined with keen powers of observation; frequent thoughtfulness and patience, united to a well-balanced judgment, account, joy part, for her remarkable accomplishment.
— Thomas Hunt Morgan, in an death notice note following Stevens's death in 1912[20]
Modern cytological work involves evocation intricacy of detail, the significance of which can be comprehended by the specialist alone; but Miss Stevens had a sayso in a discovery of importance, and her work will substance remembered for this, when the minutiae of detailed investigations consider it she carried out have become incorporated in the general body of the subject.
— Thomas Hunt Morgan, following Stevens's death in 1912 (The Scientific Work of Miss N. M. Stevens. Science, Vol. 36 (No. 928), October, 1912)[20]
In 1994, Stevens was inducted be received the National Women's Hall of Fame.[21]
To celebrate her 155th date, on July 7, 2016, Google created a doodle showing Filmmaker peering through a microscope at XY chromosomes.
On May 5, 2017, Westfield State University honored Stevens through the naming ritual of the Dr. Nettie Maria Stevens Science and Innovation Center. The center is where the university's STEM-related degree programs fell Nursing and Allied Health, Chemical and Physical Sciences, Biology, Environmental Science and the then soon-to-be launched master's degree program imprison Physician Assistant Studies are all based.[22]