Throughout history, Nobel Prizes in Physics, Chemistry, and Medicine have been awarded to individuals who have conducted groundbreaking science. This year, the Nobel Prize in Physics was awarded to three scientists for their research on black holes: Roger Penrose, Andrea Ghez (#womeninscience) and Reinhard Genzel. The award in Medicine was awarded to Harvey, J. Alter, Michael Houghton, and Charles M. Rice, for their work demonstrating that liver disease is caused by the virus hepatitis C; this is an infection that approximately 70 million people worldwide suffer from and that can now be cured with new anti-viral drugs. As for the 2020 Nobel Prize in Chemistry, it was awarded to Emmanuelle Charpentier and Jennifer Doudna (#womeninscience) for their work on genome editing. If you’re reading through these names, you probably already caught onto the fact that the majority of winners are male; in fact, out of 185 total winners of the Nobel Prize in Chemistry, only 7 are women, and only 12 women have ever won the Nobel Prize in Medicine. Furthermore, there is no documentation about whether anyone of color has ever won a Nobel Prize. But sadly, the underrepresentation of women and other minorities in science is old news – everyone knows this, and it’s something we need to be conscious of moving forward.
What we should be talking about instead is HOW ABSOLUTELY COOL the work of Emmanuelle Charpentier and Jennifer Doudna is: genome editing, accomplished with the work of CRISPR-Cas9. To start with, let’s unpack that statement a little bit. A genome is the full set of genetic information for an organism. This genetic information is stored in chromosomes, which are composed of long strands of DNA – the basis of genetic information. DNA is composed of four small molecules, called nucleotides: adenine (A), thymine (T), cytosine (C), and guanine (G). These four molecules are repeated in varying sequences along DNA, forming a code, and the order of A,T, C, and G in those sequences determines what proteins are created. These sequences, or codes, within DNA are called genes; genes control the development of embryos and are linked to your eye color, hair color, and more. And since we’re talking about Nobel Prizes and #womeninscience, I should also add that the discovery of the structure of DNA by Watson and Crick was awarded a Nobel Prize, but Rosalind Franklin (#womeninscience), who was crucial in its discovery, received no recognition.
DNA, while holding the genes for what skin color or hair color you’ll have, can also hold genes that cause diseases. Some genetically linked diseases and disorders you may have heard of include cystic fibrosis, down syndrome, sickle cell anemia, hemophilia, and Huntington’s disease. But, if DNA is a code, why couldn’t we just snip out these bad genes, and put better ones in their place? That’s where Doudna & Charpentier’s work comes in. These two women were instrumental in the discovery and implementation of a molecule called CRISPR-Cas9, which can be thought of as molecular scissors, allowing the cutting and pasting of genes. CRISPR actually comes from bacteria. The bacteria use CRISPR as a defense system to attack any invading viruses, by cutting up the genetic material of said attacking virus. CRISPR is a large protein that carries various sequences of nucleotides (these sequences are technically called crRNA, or “CRISPR –RNA”), and these sequences control where along a length of DNA CRISPR will cut, by matching up with that sequence. Cas9 is the enzyme, or protein, that cuts the DNA. In order to use CRISPR-Cas9 to control gene editing, scientists feed CRISPR the specific sequence of DNA they want to cut (this becomes the crRNA), and this directs CRISPR-Cas9 to the desired spot. Once the desired location on the DNA is cut, the cell’s own repair mechanisms will start to fix the break. If scientists want to insert a new sequence into the DNA, they provide what is called a ‘template DNA’ molecule to the cell. The cell’s own repair machinery will use this template molecule to fill in the break, creating a DNA molecule that contains the new, desired sequence! Super cool, right?
CRISPR-Cas9 has already been used to do some pretty cool things, such as remove HIV from a living organism, shrink cancer tumors in mice, and edit out the genes linked to Huntington’s disease in mice. Eventually, we may be able to use CRISPR to edit the genomes of humans, but this comes with some serious ethical concerns. For instance, at the moment, CRISPR is not perfect, and may edit the incorrect section of the genome, leading to adverse effects. Additionally, where do we draw the line of genome editing? Will it only be used to edit out disease-linked genes, or will it be used to ‘enhance’ genomes, selecting for desired traits? These are all questions we will have to grapple with as genome-editing science continues to lead to new and exciting discoveries. But for now, we can focus on celebrating CRISPR-Cas9 (World CRISPR day is October 20), and the recognition of #womeninscience.
Peer edited by Mikayla Feldbauer and Isabel Newsome