Herding Hemingway’s Cats | Kat Arney

Summary of: Herding Hemingway’s Cats: Understanding how our genes work (Bloomsbury Sigma)
By: Kat Arney

Introduction

Embark on a fascinating journey through the world of genetics with Kat Arney’s captivating book, ‘Herding Hemingway’s Cats: Understanding how our genes work’. Delve into the mysteries surrounding DNA, genes, and molecular switches. Learn about the importance of transcription and translation in protein production, the role of chromosomes, and the significance of genetic regulation in our development. As you navigate through the book’s intriguing content, you’ll find insightful connections to complex subjects like gene evolution, epigenetics, RNA, and cutting-edge advancements in genetic editing.

The Genetic Mystery of Six-Toed Cats

Ernest Hemingway’s love for six-toed cats is rooted in their polydactyl mutation, caused by a defect in the DNA control switch. The genetic code is composed of four chemical bases A, C, T, and G, which pair together in a specific sequence to form the double helix shape of the DNA molecule. Francis Crick and James Watson decoded the DNA structure in 1953, revealing the mystery behind the pairing of the chemical bases. The six-toed cats are a product of a unique mutation that leaves their genes intact, making them a fascinating genetic anomaly.

Decoding Your Genome

Your genome consists of 23 pairs of chromosomes, comprising 46 strings of DNA, which determine your traits and characteristics. Translation is the process by which messenger RNA carries protein-building instructions from DNA to ribosomes. Nature and nurture both shape us since we inherit one gene from each parent, but faulty genes from both parents can cause serious health problems.

The Complexity of the Genome

The genome is a set of genetic instructions that tell cells how to create an organism. Human beings are formed by the molecular and cellular specialization guided by these instructions. However, each person’s DNA script differs from the idealized genetic Bible for our species. Humans have fewer genes than other organisms, and their genetic diversity is low in comparison, shaped by evolution and random chemistry. The human genome is messy and contains both functional and “rubbish” DNA between genes. The first complete genome was published in 1976, while scientists sequenced the first human genome in 2001, announcing its first working draft.

Genetic Switches and Gene Activation

Molecular biologist Mark Ptashne’s research studies how genetic switches determine the activation of genes. The human genome contains different types of cells, and most human genes stay inactive until necessary. The switches outside genes control their on and off state, leading to the “genetics-as-electronics” theory. Gene regulation is vital, as the differences in switches between humans and chimpanzees lead to distinct characteristics. The ease of binding affected by the degree of “cooperativity” among these factors, adds to mutations. Misplaced and mistimed growth in developing limbs may lead to mutations, like an extra toe on a Hemingway cat due to a fault in one DNA letter among 800,000 in a gene. Gene activation depends on appropriate messaging and incorrect switching can lead to mutations, affecting other creatures’ limbs differently. Genetics influences gene activation more than gene repression, making the perfect human genome non-existent.

Rapid Adaptations in Evolution

Stickleback fish trapped in lakes developed new physical traits due to evolving genetic control switches. The lack of a “pelvis-like structure” in their spiky rear fins is the main difference from their sea-native counterparts due to them not needing the weaponry in a protected environment. Similarly, human skin color diversity has arisen due to small changes in genetic control switches affecting melanin pigment levels. Switches are responsible for the profound effects causing differences between species and their adaptations. The fast rate of genomic changes like “lactose tolerance” and technology-induced genetic adaptations may make humans more resilient, not weaker.

DNA Painting and the Exciting Nightlife of Chromosomes

Geneticist Wendy Bickmore uses a DNA painting technique to study chromosomes in the nucleus. Bickmore likens the nucleus to a city, where the center is the hub of activity and more active chromosomes congregate there. While some scientists believe that switches loop over to touch genes they control, Bickmore argues that it happens in messy “blobs” through indirect “mass action.”

Beyond Nature vs Nurture

Epigenetics blurs the line between nature and nurture by introducing ways for the environment to modify genetic code through processes like DNA methylation. Methylation can switch off genes that can be inherited by the next generation, and trauma experienced by a parent can also be passed on to their child. While cells can retain these modifications, their effects are not yet clear. Epigenetics shows that our genetic code is not set in stone and that environmental factors play a significant role in shaping who we are.

The Vitality of RNA Editing

Humans and other complex organisms have messy and junk-laden genomes compared to the efficient genomes of bacteria. Researchers Rich Roberts and Richard Gelinas used electron microscopy to study the common cold virus and discovered that virus genes work differently than bacterial genes. RNA splicing uses spliceosome proteins to eliminate noncoding text and stick protein-coding exons back together to produce different proteins. Peter Seeburg found that large-scale RNA editing takes place in neurotransmitter receptors in the brain, which is vital to brain function. ALS, a disease that causes motor neurons to die, has been linked to failed RNA editing. Gene therapies are being researched to boost motor neuron editing activity. Julia Salzman and her team investigate fusion genes that blend to create cancer-contributing combinations such as the leukemia-causing Philadelphia chromosome. Circular RNAs, scrambled messages with their ends located before their starts, exist in the brain, but their purpose is not yet understood. RNA is not passive, and flexibility arising from editing is central to brain capacity.

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