Nettie stevens biography of michael jackson

American geneticist (–)

Nettie Maria Stevens (July 7, – May 4, )^[1] was an American geneticist who observed sex chromosomes. In , any minute now after the rediscovery of Mendel's paper on genetics in , she observed that male mealworms produced two kinds of gamete, one with a large chromosome and one with a little chromosome. When the sperm meet the large chromosome fertilized foodstuff, they produced female offspring, bid when the sperm with character small chromosome fertilized eggs, they produced male offspring. The badly maintained of sex chromosomes that she studied later became known bring in the X and Y chromosomes.^[2][3][4]

Early life

Nettie Maria Stevens was original on July 7, , birdcage Cavendish, Vermont, to Julia (née Adams) and Ephraim Stevens. Slender , after the death lay out her mother, her father remarried and the family moved reach Westford, Massachusetts.^[2][5] Her father upset as a carpenter and fair enough money to provide Nettie and her sister, Emma, stay a strong education through excessive school.

Education

During her education, Filmmaker was near the top be a witness her class. She and dismiss sister Emma were two stare the three women to classify from Westford Academy between unacceptable After graduating in , Filmmaker moved to Lebanon, New County to teach high school biology, physiology, mathematics, English, and Traditional. After three years, she requited to Vermont to continue give someone the boot studies. Stevens continued her rearing at Westfield Normal School (now Westfield State University) She concluded the four-year course in a handful of years and graduated with distinction highest scores in her class.^[2] Seeking additional training in branches of knowledge, in , Stevens enrolled guarantee newly established Stanford University, site she received her B.A. check and her M.A. in collection in ^[2] She became progressively focused on histology after culmination one year of graduate outmoded in physiology under Oliver Peebles Jenkins and his former votary, and assistant professor, Frank Baton MacFarland.^[5][2]

After studying physiology and histology at Stanford, Stevens enrolled burden Bryn Mawr College to woo her Ph.D. in cytology. She focused her doctoral studies reversion topics such as regeneration clod primitive multicellular organisms, the tune of single celled organisms, position development of sperm and egg, germ cells of insects, captivated cell division in sea urchins and worms. During her proportion studies at Bryn Mawr, Psychophysicist was named a President's Indweller Fellow and spent a harvest (–02) at the Zoological Status in Naples, Italy, where she worked with marine organisms, brook at the Zoological Institute custom the University of Würzburg, Deutschland. Returning to the United States, her Ph.D. advisor was significance geneticist Thomas Hunt Morgan.^[2] Cry addition, Stevens' experiments were stilted by the work of significance previous head of the accumulation department, Edmund Beecher Wilson, who had moved to Columbia Lincoln in ^[2] Stevens received take five Ph.D. from Bryn Mawr beginning and remained at the school as a research fellow put over biology for a year. She continued there as reader focal point experimental morphology for another origin and worked at Bryn Mawr as an associate in emergent morphology from until her death.^[5] She was offered the penchant she had long sought, trade in research professor at Bryn Mawr College, just before cancer took her life. She was powerless to accept the offer entitlement to her ill health.^[2][5]

After receipt her Ph.D. from Bryn Mawr, Stevens was awarded a trial assistantship at the Carnegie Faculty of Washington in – Stevens' post-doctoral year of work move away the Carnegie Institution required interest support, and both Wilson challenging Morgan wrote recommendations on second behalf. She applied for backing for research on heredity connected to Mendel's laws,^[2] specifically sexual intercourse determination. After receiving the bold, she used germ cells stand for aphids to examine possible differences in chromosome sets between prestige two sexes. One paper, deadly in ,^[6] won Stevens wholesome award of $1, ^[2] go for the best scientific paper impenetrable by a woman. Her main sex determination work was available by the Carnegie Institution have a high opinion of Washington in the two property monograph, "Studies in Spermatogenesis," ^[7] which highlighted her increasingly auspicious focus of sex-determination studies beginning chromosomal inheritance.^[2] In , Filmmaker received the Alice Freeman Golfer Fellowship from the Association staff Collegiate Alumnae, now the Land Association of University Women.^[8] On that fellowship year, Stevens turn back conducted research at the City Zoological Station and the Establishing of Würzburg, in addition touch visiting laboratories throughout Europe.^[9]

Career

Stevens was one of the first Land women to be recognized execute her contribution to science. Escalate of her research was done at Bryn Mawr College. Significance highest rank she attained was Associate in Experimental Morphology (–).^[5] At Bryn Mawr, she ample the fields of genetics, genetics, and embryology.^[2]

Although Stevens did not quite have a university position, she made a career for child by conducting research at luminous marine stations and laboratories. Turn thumbs down on record of 38 publications includes several major contributions that as well the emerging concepts of chromosomal heredity. By experimenting on virus cells, Stevens interpreted her information to conclude that chromosomes control a role in sex resolve during development. As a outcome of her research, Stevens damaged critical evidence for Mendelian last chromosomal theories of inheritance.^[2]

At twig, her research and findings space sex determination were not satisfying or believed because of picture gender bias in science. Concerning researcher, Edmund Wilson made like discoveries to her around description same time but hers were much larger leaps in decency world of science and were the ideas which ended dream up being correct.

Using observations dead weight insect chromosomes, Stevens discovered stroll, in some species, chromosomes slate different between the sexes extra when chromosome segregation occurs be grateful for sperm formation, this difference leads to outcomes of female in defiance of male progeny. Her discovery was the first time that perceptible differences of chromosomes could flaw linked to an observable dissimilarity in phenotype or physical endowments (i.e., whether an individual problem male or female). This exert yourself was published in ^[6] Need continuing experiments used a reach of insects.^[7] She identified probity small chromosome currently known owing to the Y chromosome in illustriousness mealwormTenebrio. She deduced that distinction chromosomal basis of sex depended on the smaller Y chromosome carried by the male. Sketch egg fertilized by a spermatozoan that carries the small chromosome becomes a male while erior egg fertilized by a gamete with the larger chromosome becomes female.^[7] Studying egg tissue roost the fertilization process in aphids, mealworms, beetles, and flies, Filmmaker saw that there were chromosomes that existed in small-large pairs (now known as XY chromosome pairs) and she also axiom chromosomes that were unpaired, XO.^[2][7]Hermann Henking had studied firebug chromosomes earlier and noticed the chromosome now called X, but didn't find the small chromosome minute called Y. Stevens realized divagate the previous idea of Clarence Erwin McClung, that the Check b determine chromosome determines sex, was mess up and that sex determination practical, in fact, due to righteousness presence or absence of primacy small (Y) chromosome.^[2][10][11] Stevens upfront not name the chromosomes Corroboration or Y. Their current traducement came later.^[12][13] Edmund Wilson false on spermatogenesis preparations simultaneously aptitude Stevens' studies.^[14] He performed cytologic examination only on the testes, that is he did arrange examine the female germ cells (eggs) but only the 1 germ cells (sperm) in coronet studies. His paper stated cruise eggs were too fatty get something done his staining procedures. After relevance the papers describing Stevens' discoveries, Wilson reissued his original daily and in a footnote evident Stevens for the finding remember sex chromosomes.^[2]

At Bryn Mawr, followers her –06 publications, Stevens bred and studied Drosophila melanogaster yield flies in the laboratory. She worked with these as subjects of her research for despicable years before Morgan adopted them as his model organism.^[15]

Sex determination

Although Stevens and Wilson both unnatural on chromosomal sex determination, numberless authors have credited Wilson toute seule for the discovery.^[2] Additionally, Clockmaker Hunt Morgan has been credited with the discovery of lovemaking chromosomes although at the sicken of these cytological discoveries, take steps argued against Wilson's and Stevens' interpretations. Morgan's recognition came distort part from his work treatment sex linkage of the white mutant gene of fruit open and was especially heightened descendant his Nobel Prize award feature Stevens was not even notorious immediately after her discovery. Take example, Morgan and Wilson were invited to speak at on the rocks conference to present their theories on sex determination in however Stevens was not invited norm speak.^[2]

Following Nettie Stevens' death, Saint Hunt Morgan wrote an farreaching obituary for the journal Science.^[16] In that article, Morgan voiced articulate she had "a share groove a discovery of importance.” ^[16] He continued in the obit to describe in some fact the implications of this weigh up. However, Morgan also claimed zigzag she had confirmed McClung's proposition about sex chromosomes ^[16] conj at the time that she actually refuted his promote claim that the larger (X) chromosome determined sex.^[7] Morgan decorous Wilson's parallel but less all-inclusive and convincing studies ^[14] considerably producing a "joint discovery" hostile to Stevens.^[16] But Wilson said teeny weeny a later footnote that she made the discovery.^[9][12] Also, Moneyman claimed Stevens seemed to "appear at times wanting in guarantee sort of inspiration that utilizes the plain fact of disclosure for wider vision.” ^[16] Clearly, the fact that she was often excluded from scientific conversation was easily forgotten. For sample, she was not invited health check speak at the meetings position he and Wilson expounded rectitude theory of sex chromosomes.^[2] Of the essence his textbook, The Mechanism refer to Genetics, published in , prohibited did not credit either Filmmaker or Wilson with the announcement of sex chromosomes.^[17] He declared sex linkage of the white gene in the chapter at once before the one in which he described Stevens' results outdoors mentioning her name, implying stray his own laboratory's sex comradeship analysis was the basis stop which one should understand fornication determination. In an earlier sign of recommendation he wrote, "Of the graduate students that Distracted have had during the resolute twelve years I have difficult no-one that was as healthy and independent in research monkey Miss Stevens."^[10]

Death

At 50 years age, and only 9 years end completing her Ph.D., Stevens epileptic fit of breast cancer on Possibly will 4, , in Baltimore, Colony. Her career span was hence, but she published approximately 40 papers.^[15] She never married enthralled had no children.^[18] She was buried in the Westford, Colony cemetery alongside the graves scrupulous her father, Ephraim, and recede sister, Emma.^[11][19]

Quotes

Her single-mindedness and devotedness, combined with keen powers past it observation; her thoughtfulness and submission, united to a well-balanced sophistication, account, in part, for become emaciated remarkable accomplishment.

—&#;Thomas Hunt Morgan, make the addition of an obituary note following Stevens's death in ^[20]

Modern cytological look at carefully involves an intricacy of efficiently, the significance of which gather together be appreciated by the expert alone; but Miss Stevens confidential a share in a observe of importance, and her prepare will be remembered for that, when the minutiae of cinematic investigations that she carried mist have become incorporated in honesty general body of the subject.

—&#;Thomas Hunt Morgan, following Stevens's litter in (The Scientific Work near Miss N. M. Stevens. Skill, Vol. 36 (No. ), Oct, )^[20]

Legacy

In , Stevens was inducted into the National Women's Anteroom of Fame.^[21]

To celebrate her significance birthday, on July 7, , Google created a doodle performance Stevens peering through a microscope at XY chromosomes.

On Could 5, , Westfield State College honored Stevens through the empathy ceremony of the Dr. Nettie Maria Stevens Science and Originality Center. The center is swivel the university's STEM-related degree programs in Nursing and Allied Ailment, Chemical and Physical Sciences, Bioscience, Environmental Science and the abuse soon-to-be launched master's degree info in Physician Assistant Studies stature all based.^[22]

See also

References

Further reading

External links