Nettie Stevens
Encyclopedia
Nettie Maria Stevens was an early American
geneticist
. She and Edmund Beecher Wilson
were the first researchers to describe the chromosomal
basis of sex
.
An outstanding student, Nettie Stevens completed in two years the four-year course at Westfield Normal School (now Westfield State University) in Massachusetts. She graduated at the top of her class. At Stanford, she received her B.A. in 1899 and her M.A.
in 1900, having returned to college after an initial career as a school teacher. Stevens continued her studies in cytology at Bryn Mawr
, where she was influenced by the work of the previous head of the Biology Department, Edmund Beecher Wilson
, and by that of his successor, T. H. Morgan
. She also studied marine organisms in Europe.
Stevens was one of the first American women to be recognized for her contribution to science. Her research was done in Bryn Mawr College
. She discovered that in some species chromosomes are different among the sexes, by observations of insect chromosomes. The discovery was the first time that observable differences of chromosomes could be linked to an observable difference in physical attributes i.e. if an individual is a male or a female. This work was done in 1905. The experiments done to determine this used a range of insects, she identified the Y chromosome
in the mealworm Tenebrio. She deduced the chromosomal basis of sex depended on the presence or absence of the Y chromosome. She did not start her research until her thirties and completed her PhD
in 1903. She successfully expanded the fields of embryology
and cytogenetics
. She died on May 4, 1912 of breast cancer
, before she was able to fully take up a new faculty position.
Nettie Stevens is a somewhat controversial character. Following her death, Thomas Hunt Morgan wrote an extensive, if somewhat dismissive, obituary for the journal Science, implying that she was more of a technician than a scientist. This later assessment belies his earlier statement in a letter of recommendation: "Of the graduate students that I have had during the last twelve years I have had no one that was as capable and independent in research as Miss Stevens...". Also Nettie Stevens was the first to recognize that females have two large sex chromosomes. Wilson did not see this because he only performed tests on the testis because eggs are too fatty for the old staining procedures. Wilson even reissues his original paper and thanks Nettie Stevens for this finding. This finding is what then allowed Wilson to combine his idea of idiochromosomes with her heterosomes. This shows that Nettie Stevens was very influential in this process. Most biology textbooks credit Morgan for mapping the first gene locations onto chromosomes of fruit flies Drosophila melanogaster, but what is often missed is that it was Stevens who brought the fruit fly into Morgan's lab in the first place.
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
geneticist
Geneticist
A geneticist is a biologist who studies genetics, the science of genes, heredity, and variation of organisms. A geneticist can be employed as a researcher or lecturer. Some geneticists perform experiments and analyze data to interpret the inheritance of skills. A geneticist is also a Consultant or...
. She and Edmund Beecher Wilson
Edmund Beecher Wilson
Edmund Beecher Wilson was a pioneering American zoologist and geneticist. He wrote one of the most famous textbooks in the history of modern biology, The Cell.- Career :...
were the first researchers to describe the chromosomal
Chromosome
A chromosome is an organized structure of DNA and protein found in cells. It is a single piece of coiled DNA containing many genes, regulatory elements and other nucleotide sequences. Chromosomes also contain DNA-bound proteins, which serve to package the DNA and control its functions.Chromosomes...
basis of sex
XY sex-determination system
The XY sex-determination system is the sex-determination system found in humans, most other mammals, some insects and some plants . In this system, females have two of the same kind of sex chromosome , and are called the homogametic sex. Males have two distinct sex chromosomes , and are called...
.
An outstanding student, Nettie Stevens completed in two years the four-year course at Westfield Normal School (now Westfield State University) in Massachusetts. She graduated at the top of her class. At Stanford, she received her B.A. in 1899 and her M.A.
Master's degree
A master's is an academic degree granted to individuals who have undergone study demonstrating a mastery or high-order overview of a specific field of study or area of professional practice...
in 1900, having returned to college after an initial career as a school teacher. Stevens continued her studies in cytology at Bryn Mawr
Bryn Mawr College
Bryn Mawr College is a women's liberal arts college located in Bryn Mawr, a community in Lower Merion Township, Pennsylvania, ten miles west of Philadelphia. The name "Bryn Mawr" means "big hill" in Welsh....
, where she was influenced by the work of the previous head of the Biology Department, Edmund Beecher Wilson
Edmund Beecher Wilson
Edmund Beecher Wilson was a pioneering American zoologist and geneticist. He wrote one of the most famous textbooks in the history of modern biology, The Cell.- Career :...
, and by that of his successor, T. H. Morgan
Thomas Hunt Morgan
Thomas Hunt Morgan was an American evolutionary biologist, geneticist and embryologist and science author who won the Nobel Prize in Physiology or Medicine in 1933 for discoveries relating the role the chromosome plays in heredity.Morgan received his PhD from Johns Hopkins University in zoology...
. She also studied marine organisms in Europe.
Stevens was one of the first American women to be recognized for her contribution to science. Her research was done in Bryn Mawr College
Bryn Mawr College
Bryn Mawr College is a women's liberal arts college located in Bryn Mawr, a community in Lower Merion Township, Pennsylvania, ten miles west of Philadelphia. The name "Bryn Mawr" means "big hill" in Welsh....
. She discovered that in some species chromosomes are different among the sexes, by observations of insect chromosomes. The discovery was the first time that observable differences of chromosomes could be linked to an observable difference in physical attributes i.e. if an individual is a male or a female. This work was done in 1905. The experiments done to determine this used a range of insects, she identified the Y chromosome
Y chromosome
The Y chromosome is one of the two sex-determining chromosomes in most mammals, including humans. In mammals, it contains the gene SRY, which triggers testis development if present. The human Y chromosome is composed of about 60 million base pairs...
in the mealworm Tenebrio. She deduced the chromosomal basis of sex depended on the presence or absence of the Y chromosome. She did not start her research until her thirties and completed her PhD
PHD
PHD may refer to:*Ph.D., a doctorate of philosophy*Ph.D. , a 1980s British group*PHD finger, a protein sequence*PHD Mountain Software, an outdoor clothing and equipment company*PhD Docbook renderer, an XML renderer...
in 1903. She successfully expanded the fields of embryology
Embryology
Embryology is a science which is about the development of an embryo from the fertilization of the ovum to the fetus stage...
and cytogenetics
Cytogenetics
Cytogenetics is a branch of genetics that is concerned with the study of the structure and function of the cell, especially the chromosomes. It includes routine analysis of G-Banded chromosomes, other cytogenetic banding techniques, as well as molecular cytogenetics such as fluorescent in situ...
. She died on May 4, 1912 of breast cancer
Breast cancer
Breast cancer is cancer originating from breast tissue, most commonly from the inner lining of milk ducts or the lobules that supply the ducts with milk. Cancers originating from ducts are known as ductal carcinomas; those originating from lobules are known as lobular carcinomas...
, before she was able to fully take up a new faculty position.
Nettie Stevens is a somewhat controversial character. Following her death, Thomas Hunt Morgan wrote an extensive, if somewhat dismissive, obituary for the journal Science, implying that she was more of a technician than a scientist. This later assessment belies his earlier statement in a letter of recommendation: "Of the graduate students that I have had during the last twelve years I have had no one that was as capable and independent in research as Miss Stevens...". Also Nettie Stevens was the first to recognize that females have two large sex chromosomes. Wilson did not see this because he only performed tests on the testis because eggs are too fatty for the old staining procedures. Wilson even reissues his original paper and thanks Nettie Stevens for this finding. This finding is what then allowed Wilson to combine his idea of idiochromosomes with her heterosomes. This shows that Nettie Stevens was very influential in this process. Most biology textbooks credit Morgan for mapping the first gene locations onto chromosomes of fruit flies Drosophila melanogaster, but what is often missed is that it was Stevens who brought the fruit fly into Morgan's lab in the first place.