Queen of X and Y : Nettie Marie Stevens

How are genders revealed? What determines the characteristics that make women women and men men? I'm sure many of you have heard of the concepts x and y in biology class. These things we call X and Y are our sex chromosomes. These chromosomes contain switches that trigger the regulation of sex hormones that determine sexual characteristics in males and females. Women carry XX chromosomes and men carry XY chromosomes. So how did these X and Y first appear?

What Was the Concept of Gender in Ancient Times?

Until the 20th century, many theories have been put forward about what the factor that determines the sex of the baby is. The ancient Greek philosopher Aristotle thought that the temperature during fertilization was effective in making the child a boy. He even advised people who want male heirs to make love in the summer. Because she thought that if the man could not provide enough passion and fire, at least the temperature of the air would be effective in making the baby a boy.

At that time, in the scientific world: After the death of Gregor Mendel, scientists who rediscovered his work were investigating the mechanisms of how traits are passed on between generations, including sex determination.

Nettie Marie Stevens, First American Biologist and Geneticist

Nettie Marie Stevens was born on July 7, 1861, in Vermont, USA. Nettie, who was the person who brought the X and Y chromosomes to the scientific world in his research on the chromosome structure in 1905, studied at many different universities. She completed her school life with the savings she gained by teaching on the one hand. Nettie Marie Stevens, who has been working in different fields as well as her education, started to do her first scientific studies after the age of 35 and completed her doctorate education at Bryn Mawr University.

In 1906, he discovered that male insects produce two types of sperm, one with a large chromosome and the other with a small chromosome. Working with mealworms, Nettie observed that when sperms with large chromosomes are fertilized with eggs, they produce female offspring, while sperm with small chromosomes produce male offspring. Thanks to this invention, it has been proven that gender is determined genetically.

Unfortunately, the attitude towards women scientists at that time also affected Nettie. Nettie's discovery is not immediately accepted. At the time, it was believed that gender was determined by maternal and/or environmental factors. At that time, Edmund Wilson made a similar discovery. With this discovery, the genetic basis of gender formation is attributed to Thomas Hunt Morgan, one of the leading geneticists of the time, and it is recorded in textbooks and the history of science in that way. Morgan even contemptuously writes in Science magazine that Stevens behaved more like a technician than a real scientist throughout the experiment.

Morgan, the author of the first genetics textbook, wanted his contributions to the field to grow, according to Hoopes of the College. Stating that textbooks tend to take other existing books as their source, Hoopes says that for this reason Stevens' contributions to his field are neglected. Part of the reason why Morgan thinks he owes Stevens is that, unlike many researchers with whom Morgan corresponded about his theories at the time, in his correspondence with Stevens he wanted to learn the details of his experiments. After Stevens' death, he wrote to Morgan Science that Stevens did not have a broad vision of science; “He never asked Stevens about his vision,” Hoopes explains.

Nettie Marie Stevens, who introduced the concept known as X and Y chromosomes to the literature today, continued her scientific life, which started at the age of 35, until the age of 50. The scientist, who learned that he had breast cancer in addition to the health problems he had in his last years, died on May 4, 1912 in Baltimore, USA, after his worsening illness. With the ongoing studies after its discovery, many researches on genetics are carried out and important results are obtained.