Albert Einstein, Isaac Newton, Charles Darwin… now name me a famous female scientist… I don’t know about you but I get to Marie Curie then draw a blank. According to Smithsonian, an american science magazine here are “10 Historic female scientists you should know”. Ok, I recognise the name “Rosalind Franklin” I’ll give you that but I’d never heard of any of the other women and I’m a final year biology student for goodness sake.
I’m sure we’re all aware getting published as a female back in the day was not an easy feat which could begin to explain our apparent absence from textbooks and papers (who am I kidding, from the internet). However I think it’s important to recognise despite all the odds stacked against these women during the 19th and 20th Century their love of science pushed through and I think we all owe them much more than we realise.
To give these Women the credit they deserve I’ve decided to dive into the depths of the internet to provide you with all the information I can on their discoveries, theories and contributions to science.
So let’s start the roll call, I’ve already shown off that I recognise her name so it seems only right to start with….
Name: Rosalind Franklin (1920-1958)
Contribution: structure of DNA and viruses and fine structure of coal and graphite
Quote: “Science and everyday life cannot and should not be separated.”
Her most famous contributions were her X-ray diffraction images of DNA that when shown to Watson by her lab partner sparked his understanding of the structure of DNA and the classic double-helix structure we know today.
DNA double helix [Source: Wikimedia Commons]
THE DNA DOUBLE HELIX
DNA is the genetic code found in nearly all organisms. A lot of this DNA is the same even between seemingly different organisms for example humans share nearly 50% of their DNA with….wait for it….bananas. DNA encodes for all the proteins and enzymes in your body that lead to the formation of our organs and processes such as breathing. What I’m trying to get at here is we owe a lot to DNA and as biology goes it’s pretty key.
During fertilization it is the DNA from the egg and sperm that join to form the miracle that is you. Now it may seem a bit arrogant to refer to yourself as a ‘miracle’ but if I told you the likelihood of you existing is just as likely as throwing one life saver ring into all the oceans, there being only one turtle in all these oceans and his head poking through the ring on the first go then yeh, I think you’re justified in calling yourself a miracle.
Physics Research Students, Cavendish Laboratory, Cambridge. James Watson & Francis Crick first row 6th and 7th from left respectively. [Source: Wikimedia Commons]
Firstly before we look at how Franklin’s work contributed to the famous double helix structure let’s review a quick summary on the structure of DNA:
DNA is made up of different nucleotides that each contain a phosphate, sugar and a base (the base is either G,T,C or A). These nucleotides join together via a covalent bond between the phosphate group of one nucleotide and a carbon on the sugar of another nucleotide.
Two nucleotides joining together via a covalent bond (or phosphodiester bond) [Source: Wikimedia Commons]
Lots of nucleotides join together to form a strand. Another strand containing the exact same nucleotides is also made and runs anti-parallel to the first strand. So Watson and Crick knew this much and this is where Rosalind’s X-ray images come in.
Franklin’s X-ray Diffraction Image. The DNA helix image is the B-DNA image on the right. [Source: Wikimedia Commons]
This image was presented to Watson & Crick in 1952 and is known as the “B-form”. It is a much clearer images than others of the time as water was added to the DNA sample. The X-shape of the image was a tell tale sign of a helical shape. As the X-ray pattern is so regular the dimensions of the helix must be constant i.e. the diameter of the helix will stay the same all the way down the helix. Comparing this B-form to the A-form Rosalind and Maurice were able to determine some basic dimensions of the helix. This site explains the specific dimensions they were able to calculate and thus was born the famous DNA double helix.
Here is a very nifty video explaining the work of James Watson, Francis Crick and Maurice Wilkins and how Rosalind Franklin contributed to the discovery.
Contribution: Genetics of maize, homologous recombination and transposition.
Quote: “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.”
Barbara McClintock contributed a lot to our understanding of genetics. Her theories on how genes worked didn’t match with what was believed at the time. Often called a “maverick” and rarely taken seriously it wasn’t until 1983 (56 years after her work with maize first started) that scientists had the equipment and knowledge to understand her theories at which point she was awarded the Nobel Prize for Physiology and Medicine. She did admit finding it difficult to explain her theories and found it frustrating that others couldn’t understand what was so obvious to her – I bet that quote above came in very handy.
First of all let’s look at her discovery of transposable elements.
Transposable elements are sequences of DNA that move from one what part of the genome and insert themselves in a different part of the genome. This can cause or reverse genetic mutations and can change the size of the genome. When it comes to transposable elements there are retrotransposons and DNA transposons. Retrotransposons are sequences of DNA that need to be converted from RNA to DNA by reverse transcription whereas DNA transposons do not. The transposable elements that McClintock focused on were DNA transposons.
DNA transposition [Source: Wikimedia Commons]
These ‘transposons’ or ‘transposable elements’ move themselves from one part of the genome to another via the enzyme transposase, the DNA sequence in question encodes for the transposase enzyme itself.
Insertion sequence of a DNA transposon [Source: Sogeking – user, Wikimedia Commons]
Transposons have inverted terminal repeats at either end and an open reading frame in the middle. The open reading frame encodes for the genes that will be moved from one part of the genome to another but also certain structural genes such as transposase, the enzyme that enables the movement of the transposon by a ‘cut and paste’ mechanism.
This is just a small section of McClintock’s work, more of her work can be read here.
Contribution: Banning of pesticides and first true environmentalist
Quote: “But man is a part of nature, and his war against nature is inevitably a war against himself.”
Rachel Carson was an american conservationist and marine biologist. Famous for her literature (The Sea Around Us, The Edge of the Sea & Silent Spring). Carson’s main belief was the damage that pesticides or ‘biocides’ as she called them had on the environment. A commonly used pesticide at the time was DDT (dichlorodiphenyltrichloroethane…I can’t say it either). It was first synthesised in 1869 and wasn’t used as an insecticide until 1939. DDT is made by a reaction between chloral (a colourless oily liquid sometimes used as a hypnotic substance) and chlorobenzene (a colourless, flammable liquid often used as a solvent for the production of other chemicals). These two liquids form DDT in the presence of sulfuric acid. The way DDT kills insects is fairly impressive but cruel (here is a video from 1946 on how it works, the commentator is a tad too indifferent to the death of the fly if you ask me). The chemical causes sodium channels within the insect’s neurons to open. This causes random firing of neuron signalling leading to spasms and eventually death. However, this video shows just how chuffed those of 1946 were to use it to prevent polio in children. At this point in time DDT was seen as no less than a miracle. During a typhus outbreak in 1943 in Naples military police officers sprayed it over thousands and typhus was removed seemingly overnight. However despite the huge support for DDT across the globe Carson noticed the detrimental effect it was having on the surrounding wildlife. DDT is sprayed onto crops to kill crop eating insects. However this often kills insects that don’t effect crops and the toxic substance can quite easily enter the food chain and harm a wide array of organisms from microorganisms to humans. Here is how DDT can affect all parts of the food web:
Microorganisms: One way DDT spreads is by bioaccumulation, bioaccumulation is the accumulation of a substance within an organism where it absorbs the substance faster than it loses it (thankyou Wikipedia). Bioacculumation often occurs in algae as the substance is able to come into greater contact with an organism when it is in water. Rather than dying algae keeps the substance within itself and seeing as algae is the start point for a number food chains this can have a number of detrimental effects on a number of organisms.
Invertebrates: Terrestrial invertebrates such as molluscs and worms are pretty tough when it comes to DDT, they can tolerate a large amount for a long period of time. However the substance is still within their system and can be passed on to their predators. A process known as biomagnification. Aquatic invertebrates however are highly sensitive to DDT especially while they are still young. This can effect their development and reproduction as well as their nervous system.
Fish: It is clear that DDT causes problems in fish but exactly how this happens we don’t really know. We think the chemical once inside the fish messes up it’s normal biological processes often leading to death.
Birds: DDT is most famous for its effect on birds. A certain form of DDT known as DDE is known to cause egg shell thinning as it alters certain enzymes used for reproduction. One of these reproductive enzymes is responsible for the production of calcium in egg shells. By disrupting this enzyme eggshells contain less calcium, are thinner and are much easier to break.
Humans: The initial use of DDT seemed to pose no threat to humans as it was unable to be effectively absorbed by human skin. As shown in the video above (and the image below) it was sprayed everywhere.
A US soldier demonstrating DDT hand-spraying equipment. [Source: Wikimedia Commons]
However over time people started to realise that DDT was staying in their bodies. Within the body it is stored in fatty organs such as adrenals, testes and thyroid. For this reason it was especially prominent in breast milk. In 1968 it was recorded that the average american was taking in 0.025 milograms of DDT per day. Research shows 6-10 mg/kg in the body leads to nausea, headaches, vomiting, confusion and tremors and any concentration above 236 mg/kg can kill. Facts such as these were unveiled in Carson’s book as well as linking DDT to other health problems such as breast cancer. Opening up people’s eyes to the effect this chemical had on wildlife and themselves was crucial at this time. It seems the publication of Silent Springs really was a life saver!
I thought it would be a good idea to discuss the work of a female scientist who is still living just to show there are always new things to be discovered/created/discussed!
Name: Jane Goodall (1934-present)
Contribution: Study of chimpanzee social and family life
Quote: “Change happens by listening and then starting a dialogue with the people who are doing something you don’t believe is right.”
Jane Goodall’s TED talk on our similarities with chimpanzees, how we have harmed our environment and what we can do to improve the environment with her organisation “roots and shoots”. I would like to note she is aged 68 in this video…68! (I’m gunna start a career with chimpanzees…)
*If you’re in a hurry a lot of the meaty detail doesn’t come in until 7 minutes 45 seconds.*
Anyone new to TED talks I strongly encourage you to visit their website now! They release incredible videos on all topics that will shock, inspire and pretty much question everything you know. I cannot recommend it enough.
The synopsis mentions a “missing link” between humans and chimpanzees. Anyone who has read The Accidental Species by Henry Gee will have cringed at this just as much as I did. The media often explains evolution as a progression from one organism to the next with each organism ‘improving’ and culminating in the incredible Homo sapiens!! (us). Henry Gee’s book completely disagrees with this well known perception. Anyone who is interested in evolution just like the TED talks this will also make you question everything you have ever known, but who are scientists if not those who question!
Goodall’s study of the Kasakela chimpanzee community in Gombe Stream National Park, Tanzania forced us to reevaluate the way we view chimps. Her methods of analysing the chimps were different to those of the time; instead of numbering the chimps she gave them names such as Fifi and David Greybeard. Her hard work led her to be able to challenge two long-standing beliefs in the zoological community at the time. 1) Humans were the only species to use tools and 2) chimps were vegetarian. She was able to challenge these theories with images such as this:
Chimp extracting termites from a termite mound using a stick. [Source: Wikimedia Commons]
Additionally she showed the apparent emotional relationships formed between individuals with behaviours such as kissing, hugging and even tickling. All this evidence suggested that chimps bared a similarity to humans not only in their genes but in their behaviour.
Where the Women at?! 