Mendel, Fruit Flies, and Me
by Susan Bradford
At Paul D. Schreiber High School in 1960, each person in Mr. Martinson’s biology class had to do a big project or research paper in the spring. This project had to be ongoing, in-depth, and would count for a large part of our grade. Somehow, I decided it would be interesting to “prove” Mendel’s laws of genetics. Actually, I was going to try to replicate some of the patterns Gregor Mendel had predicted would occur in pea varieties.
I ordered various strains of drosophila, fruit flies, from the Cold Spring Harbor Lab where my good friend Betsy’s sister worked. I decided upon ordering three varieties: regular red-eyed fruit flies, white-eyed fruit flies, and dumpies (fruit flies with very short wings) because I thought those varying characteristics would make it fairly easy to distinguish one from the other.
I visited neighbors who had babies in order to collect a lot of glass baby food jars to hold the assorted groups of flies and their food. I used instructions to mix up an agar and fruit medium as food to put in the bottles. Then I put fruit flies with one pure type into certain bottles, and each of the other types in other bottles, and counted what I had. In the days to follow, I would keep track of each generation. I used a plan about crossing the strains in certain ways. Then I had to observe and count the first generation of flies produced and, after that, the second and third generations of flies to see which and how many inherited the red eyes, white eyes, short wings or long wings.
It was fascinating, but counting them was difficult and involved using liquid ether to put the flies temporarily to sleep. Once etherized, I could empty the flies onto a piece of white paper in order to closely observe the characteristics, separate the flies into groups, and count them. From our local pharmacy, I purchased a can of ether that my mother made me store in our garage since it was so volatile.
Ether has a very strong and distinctive, rather sweet and sickly smell that I may never forget. I actually became light-headed sometimes as I bent over to count the flies. The counting was tricky because you had to use enough ether to put the flies to sleep for the entire time it took to count and sort them but not so much that it would kill them. I knew this was important but had no idea of the amounts to use. Naturally, several weeks into this project, I did not use enough ether, and after carefully counting and sorting the tiny fruit flies, hundreds of them woke up and flew off. We had fruit flies everywhere in the house for a long time. Sitting down to dinner, in the living room, or taking a bath, my family and I would be besieged by tiny black spots before our eyes. But the worst part was that I had to begin my experiment all over again.
Luckily, I had set aside enough of the “pure” flies of each variety that I was able to begin again without delay. Not surprisingly, the next time, as I emptied the etherized flies onto the paper, I noticed that their little wings were at right angles, which was not good. I had killed that entire batch because I wanted to be certain they would not wake up in the middle of counting again. Finally, I figured it out and was able to etherize them properly. Over the next several generations of flies, I was able to do it correctly and ended up with a very successful project. My numbers came out very close to what would have been predicted using Mendel’s laws.
My teacher was pleased and gave me a good grade.
I was happy because I felt as if I were a real scientist, and I have memories I will keep.
My parents were probably just glad I did not knock myself out or blow up the house.
| Mendelian inheritance is a set of primary tenets relating to the transmission of hereditary characteristics from parent organisms to their children;The laws of inheritance were derived by Gregor Mendel, a 19th century monk conducting hybridization experiments in garden peas. Between 1856 and 1863, he cultivated and tested some 29,000 pea plants. From these experiments he deduced two generalizations which later became known as Mendel’s Laws of Heredity or Mendelian inheritance. He described these laws in a two part paper, Experiments on Plant Hybridization that he read to the Natural History Society of Brno on February 8 and March 8, 1865, and which was published in 1866. Wikipedia|
 Cold Spring Harbor Laboratory (CSHL) is a private, not-for-profit research and education institution at the forefront of efforts in molecular biology and genetics to generate knowledge that will yield better diagnostics and treatments for cancer, neurological diseases and other major causes of human suffering. Home to seven Nobelists, the laboratory was founded in 1890 as one of the first
Home to seven Nobelists, the Laboratory was founded in 1890 as institutions in the world to specialize in genetics research. CSHL has played a pivotal role in the emergence of molecular genetics, the scientific foundation of the contemporary revolution in biology and biotechnology. At CSHL in 1953, James D. Watson presented his first public lecture on his and Francis Crick’s discovery of the double-helical structure of DNA, for which each later won a Nobel Prize. As director and then president of the Laboratory from 1968 to 2003, Watson was instrumental in developing CSHL into one of the world’s most influential cancer research centers. www.cshl.ed
Susan Bradford was a teacher and administrator who retired from Maimonides School in Brookline and has been a longtime BOLLI member since then. She has led several history related courses and been active on various BOLLI committees. This piece was first written in a BOLLI writing class led by Ruth Harriet Jacobs.