About Critical Values

Genetics is the scientific study of genes and heredity—of how certain qualities or traits are passed from parents to offspring,¹ and women have been a part of it since the beginning. As genetics reveals new diagnostic and therapeutic frontiers,² we get to know more about ourselves as individuals and as a species.  

Cytogenetics is a branch of biology focused on the study of chromosomes and their inheritance.³ This field has evolved a lot over the past few decades,⁴ and much of the research advancements have taken place in research laboratories where women make up a large part of the workforce. Like many other fields, women are underrepresented in scientific research and publication and often underpaid.⁵ But despite all the obstacles, women have made major contributions with discoveries that shaped the progress in many scientific fields.⁶ Here is a brief overview of a few women who have made major contribution in the field of cytogenetics.  

Rosalind Franklin (1920-1958) 
Rosalind Franklin was a British scientist who played a crucial role in understanding the structure of DNA.⁵ While an undergraduate, she wrote, “Science and everyday life cannot and should not be separated. Science, for me, gives a partial explanation of life.”² 

Franklin's expertise in X-ray crystallography, particularly her data, including "photo 51," played a crucial role alongside James Watson and Francis Crick's own findings in publishing the discovery of the double helix DNA structure in 1953. Her contribution was acknowledged posthumously in Watson’s memoir in 1968.⁶ 

She did ground-breaking work on viruses at Birkbeck College, until her death of ovarian cancer at the age of 37. Her contributions to the discovery of DNA structure became better understood in the decades following her death, as biographies and documentaries highlighting her life and career gained public attention.² 

Nettie Stevens (1861-1912) 
Nettie Stevens was an American geneticist credited with the discovery of sex chromosomes, who began her career as a research scientist at the age of 39.^2,5 During her graduate studies, she developed an interest in histology, physiology, and cell division and regeneration.  

Studying the mealworm, Stevens found that males made reproductive cells with both X and Y chromosomes, whereas females made only those with X.⁵ From this, she deduced that sex is a chromosomal characteristic, inherited from the father. This countered prevailing beliefs at the time that sex was determined from maternal or environmental factors.   

Barbara McClintock (1902-1992)

Barbara McClintock was a 20th century American cytogeneticist who is the only woman to receive an unshared Nobel prize in Physiology or Medicine. McClintock dedicated her work to cytogenetics and discovered mobile genes. From studying maize, McClintock identified and characterized transposable elements also known as ‘jumping’ genes. This revolutionized the field as it revealed that an organism’s genome is not static.5 

McClintock's research faced skepticism in the 1950s, with the community only recognizing its significance in the late 1960s. 

McClintock loved working in the lab and once said: “I was just so interested in what I was doing I could hardly wait to get up in the morning and get at it.”⁷ Throughout her career, McClintock studied the cytogenetics of maize, making discoveries so far beyond the understanding of the time that other scientists essentially ignored her work for more than a decade. But she persisted, trusting herself and the evidence under her microscope.⁷ 

As she once said, “If you know you are on the right track, if you have this inner knowledge, then nobody can turn you off... no matter what they say.”⁷ 

Elizabeth Blackburn (b.1948) 

Elizabeth Blackburn is a self-described “lab rat” who became an explorer in the realms of health and public policy. She discovered the molecular structure of telomeres and co-discovered the enzyme telomerase, essential pieces in the puzzle of cellular division and DNA replication. Her research sparked advances in cancer treatment, decoded mysteries of aging as well as biological links between life circumstance and lifespan. Wherever her curiosity leads her, Blackburn emphasized that every conclusion be backed with data. “You have to get the science right.”⁸ 

She focused her telomere research on Tetrahymena, one-celled organisms with ample linear chromosomes (and hence telomeres). In sequencing their DNA, Blackburn discovered that telomeres are composed of 6 short repeating segments of DNA.⁸ In 1984, with her student Carol Greider, Blackburn discovered telomerase, an enzyme that lengthens each strand of DNA before the copying stage, compensating for the shortening during cell division.⁸ 

Janaki Ammal (1897-1984) 

Janaki Ammal was an Indian botanist who worked on plant breeding and cytogenetics. She was the first woman to obtain a PhD in botany in the United States, and her work on chromosome numbers and ploidy shed light on the evolution of species and varieties.⁵ 

Charlotte Auerbach (1899-1994) 

Charlotte Auerbach was a German Jewish geneticist, most known for founding the study of mutagenesis. Auerbach wrote 91 scientific papers and received the Darwin Medal in 1976,⁵ and her work on drosophila showed that mustard gas could induce mutations.  

Martha Chase (1927-2003) 

Martha Chase was an American geneticist and was one of the scientists who confirmed that DNA is the genetic material of life. Chase and Alfred Hershey used the renowned Hershey-Chase experiment in a series of experiments to confirm that DNA, not protein, was responsible for carrying and transmitting genetic information. Chase’s work did not earn her much recognition, however, and only Hershey received the Nobel Prize in Physiology or Medicine for their discovery.⁵ 

Mary Frances Lyon (1925-2014) 

Mary Frances Lyon was a British geneticist, most known for her discovery of X-chromosome inactivation. Undeniably, her discovery of this phenomenon has had profound implications for clinical genetics and developmental biology.⁵ 

The history of science is one where women have been a part of every major progress.⁶ These are just a few of the amazing women who have helped advance the field of genetics. It is important that we continue to recognize their achievements, so we inspire the next generation of female scientists. It is important that young women see a reflection of themselves within the scientific community.  

Mattel company released six Barbie dolls to honor women in science and their contributions in the fight against COVID-19 in 20219 depicting real and successful women scientists as role models for our future generations.⁶ In 2020, two women, Emmanuelle Charpentier and Jennifer A. Doudna, shared the Nobel Prize in Chemistry for their work on DNA editing, the only science Nobel to be won by two women. The legacy of all of these notable women must continue.  

References 

1. National Institute of General Medical Sciences, National Institutes of Health. Genetics. May 4, 2022. https://nigms.nih.gov/education/fact-sheets/Pages/genetics.aspx. Accessed January 9, 2023. 

2. The Women in Medicine Legacy Foundation. Women pioneers in genetics: moving the field forward. May 4, 2021. https://www.wimlf.org/blog/women-pioneers-in-genetics-moving-the-field-forward. Accessed January 9, 2023. 

3. “Cytogenetics.” Genome.gov, https://www.genome.gov/genetics-glossary/Cytogenetics. 

4. Chial H. Cytogenetic methods and disease: flow cytometry, CGH, and FISH. Nature Education. 2008;1:76. 

5. Gunn S. Women in genetics. Front Line Genomics. September 8, 2020. https://frontlinegenomics.com/women-in-genetics/.Accessed January 9, 2023. 

6. Elbardisy H, Abedalthagafi M. The history and challenges of women in genetics: a focus on non-Western women. FrontGenet. 2021;12:759662.  

7. Barbara McClintock: Nobel Prize in Physiology or Medicine 1983. Women Who Changed Science. https://www.nobelprize.org/womenwhochangedscience/stories/barbara-mcclintock. Accessed January 9, 2023. 

8. Elizabeth Blackburn: Nobel Prize in Physiology or Medicine 2009. Women Who Changed Science. https://www.nobelprize.org/womenwhochangedscience/stories/elizabeth-blackburn. Accessed January 9, 2023. 

9. Joly J, Lawrence S. Life in plastic, it’s fantastic! COVID vaccine scientist gets Barbie. EuroNews. April 8, 2021. https://www.euronews.com/next/2021/08/04/life-in-plastic-covid-19-vaccine-scientist-honoured-with-barbie-doll. Accessed January 9, 2023.