One of the stories in the book, the discovery of the gene that caused Huntington’s disease, moved me tremendously when I first read it a few years ago. It’s the perfect example of the amount of effort that goes into a scientific discovery that then ends up as a single sentence in a textbook; in this case, that Huntington’s disease is a hereditary, neurodegenerative disorder caused by a mutation in a single gene.
The story of finding that mutation would make a thrilling movie: a young woman named Nancy Wexler, devastated by the news that her mother has been diagnosed with Huntignton’s and that she and her sister would have a 50-50 chance of getting it, decides to devote her life to solving this medical mystery. Her quest takes her from nursing homes in Los Angeles to interdisciplinary scientific workshops in Boston to stilt villages surrounding Lake Maracaibo in Venezuela. Her decade-long blood and skin sample collection efforts there would create the largest family tree with Huntington’s, leading to the first genetic test for the disease, followed by locating the precise genetic mutation that caused it.
The gene sequence had a strange repeating structure, CAGCAGCAG… continuing for 17 repeats on average (ranging between 10 to 35 normally), encoding a huge protein that’s found in neurons and testicular tissue (its exact function is still not well understood). The mutation that causes HD increases the number of repeats to more than forty – a “molecular stutter” – creating a longer huntingtin protein, which is believed to form abnormally sized clumps when enzymes in neural cells cut it. The more repeats there are, the sooner the symptoms occur and the higher the severity.
Nancy herself opted not to take the genetic test she helped create. “If the test showed I have the gene,” she wrote in 1991, “would I continue to feel the happiness, the passion, the occasional ecstasy I feel now? Is the chance of release from Huntington’s worth the risk of losing joy?”. In 2020, at the age of 74, she revealed that she had Huntington’s. The public acknowledgment was not a surprise for those close to her – for the last decade, they noticed her gait slowly deteriorate, speech slur, and limbs jerk in random directions, the same characteristics she saw in her mother half a century ago, and in the hundreds of Venezuelan patients she tended to ever since.
The more you explore, the more astonishing it gets. Suddenly, you’re surrounded by these facts that stop you in your tracks. Like the fact that there are 20-30 trillion red blood cells in our body, making up roughly 84% of all our cells, and 1.2 million are created in our bone marrow every second. Or the fact that our visual system is predictive, calculating where to move the hand to catch a ball before your visual system has fully registered its trajectory.
One of my favorite ‘sentences that stopped me in my tracks’ comes from Nick Lane’s book, The Vital Question. He starts with carefully explaining that all cells derive their energy from a single type of chemical reaction, the redox reaction, where electrons are transferred from one molecule to another. Rust is a redox reaction: iron donates electrons to oxygen, being oxidized in the process. Same with fire: oxygen (O2) is reduced to water after receiving two electrons (O2-) and then two protons (H2O), balancing the charges, and releasing heat in the process. Respiration — the process that turns our food into energy — does exactly this as well, except that it conserves some of the energy in the form of a molecule called adenosine triphosphate (ATP). Think of ATP as an energy currency, able to be stored or converted back into energy by splitting the molecule into ADP (adenosine diphosphate) and Pi (phospate). And so, he writes, “in the end respiration and burning are equivalent; the slight delay in the middle is what we know as life.”
Nehal Udyavar
https://nehalslearnings.substack.com/p/i-should-have-loved-biology-too