Indholdsfortegnelse for Understanding Genetics 2024 i Understanding Genetics

The field of genetics is remarkable in that it holds the key to our past and future. Comprised of DNA sequences, our genes demonstrate how life forged pathways and evolved into the creatures and plants we know and love on Earth today. Strings of genetic code can also hold power over us in the form of viruses, mutations leading to cancer, and more; however, we are beginning to harness genetics to fight back using remarkable leaps in genetic science, producing vaccines and powerful gene therapy. In this bookazine, we’ll take you through the world of genetics to help you understand this crucial avenue of science. Enjoy!…

In 2015, Tomas Lindahl, Paul Modrich and Aziz Sancar received the Nobel Prize in Chemistry for their work on DNA repair. Our DNA is under assault from the environment. Ultraviolet light sticks DNA bases together and cigarette smoke causes mutations. When a cell divides, it makes copying errors. The separate work of these scientists delved into the machinery that finds this damage and fixes it. Lindahl discovered ‘base excision repair’, a process that cuts errors from the genome and remakes them. Sancar found a system called ‘nucleotide excision repair’, which removes and fixes errors that make the DNA bulge. Modrich identified DNA ‘mismatch repair’, which fixes areas where bases on opposite strands don’t match up. DNA damage DNA accumulates errors over time. Some occur when cells make copying mistakes. Others are…

1859 Charles Darwin publishes On the Origin of Species, describing how life evolves through natural selection. “They base their breakthrough on the work of dozens of other scientists” 1879 Walther Flemming Flemming becomes the first person to observe cell division, or ‘mitosis’. He dyes salamander DNA with a chemical called aniline. He then watches as the chromosomes in the nuclei turn into thick threads, which line up across the middle of the cell. The threads then separate into two groups, and the cell splits in half. 1865 Gregor Mendel Mendel, a monk, presents his work on dominant and recessive genes after performing experiments on nearly 30,000 pea plants. He cross-pollinates pea plants to find out how traits like colour and texture pass from one generation to the next. He discovers…

Upload yourself There may come a point when attempts to prevent ageing turn from the biological to the digital. If you truly want to live forever, then uploading your brain may be a real option in the future. When, however, remains unclear. The science is called Whole Brain Emulation (WBE), and in theory, it would involve uploading your consciousness into a computer, including all of your thoughts and feelings. However, the first and biggest hurdle scientists face is mapping the human brain. There are roughly 86 billion neurons in your head and each neuron can connect to 10,000 other neurons. Thus far, scientists have only been able to map the 302-neuron brain of a nematode, so we’re a long way off navigating the human mind. Nevertheless, many tech companies and…

For around 3.7 billion years, life has followed a roadmap of evolution. The journey to modern-day life and the more than 2.16 million known species that reside on Earth has been guided by several different evolutionary pathways. The naturalist known as ‘the father of evolution’, Charles Darwin, first proposed the theory of evolution by natural selection after he jumped aboard the HMS Beagle in 1831 and sailed around the world for five years. On his travels, he discovered diverse wildlife, observing that they had anatomy specially adapted to their environments. He concluded that a species’ survival depends on traits that suit its environment. This survival-of-the-fittest approach means that only animals with beneficial characteristics can continue to reproduce and pass them on to their offspring. Darwin proposed that through forces of…

This is perhaps one of the biggest misconceptions about evolution – that humans are descendants of modern monkeys or apes. It may be that the well-known ‘evolution of man’ image, showing a series of apes that become ever-more upright and human-like, has helped to spread this myth. Monkeys and apes are not the same thing. Modern monkeys are divided into New World and Old World monkeys, both of which are separate groups of species to apes. The apes are then divided again into lesser apes (gibbons) and great apes – which include humans. So we aren’t descended from monkeys, but what about apes? We share many traits with the other great apes – chimpanzees, orangutans, bonobos and gorillas – and they are our closest living relatives. But they’re not our ancestors,…

Evolution can tell us a lot about why life is the way it is and how life changes and adapts over time, but it doesn’t claim to explain how it started. Evolution has taken us back to LUCA: the Last Universal Common Ancestor – the organism from which all life on Earth evolved. Comparing the genes of organisms in the two most ancient branches of the tree of life (archaea and bacteria), it’s estimated LUCA lived around 3.8 billion years ago and had at least 100 genes. Evolution can give us clues about what was required for life to begin, but this puzzle has not yet been solved and is being tackled by scientists across many fields. Primitive life One of the most compelling ideas is that life began in the…

It was assumed that irrational fears are learned through personal experience or taught to us by others. However, it is now thought that some phobias have a genetic origin. For example, identical twins are more likely to share the same fears than non‑identical twins, even if they are raised apart. Experiments with mice have shown the fears they develop can be passed down to their children and even their grandchildren. The mice were conditioned to fear the scent of acetophenone – a sweet-smelling chemical. Researchers found that the pups, and even the grand-pups, of the conditioned mice, were startled by the scent, too. One explanation could be that parent mice communicate with their pups to teach them what to fear. Studies have found that when mice are scared, they release…

Humankind’s canine companions and feline friends belong to an order of animals called Carnivora. They are the descendants of the first mammals of the late Paleocene epoch that hungered for the flesh of other animals. Between 65 and 35 million years ago, an order of weasel-like animals called Miacis skulked through the trees of ancient woodlands across Eurasia and North America. These furry mammals were arboreal creatures, meaning they spent their time hunting among the lush vegetation of the Paleocene forest. Although Miacis was one of the earliest carnivorous mammals on Earth, it was by no means the most ferocious. Following the extinction of the dinosaurs around 66 million years ago, two mammalian hunters rose to the top of the food chain: wolf‑like predators called creodonts and the hoof-footed ancestors…

DNA and mRNA vaccines are two new forms of vaccine (relatively speaking) which represent exciting advancements in medical science, harnessing the power of our cells and our immune systems to fight against various diseases. DNA vaccines, as the name suggests, introduce a small piece of DNA directly into our cells, which contains instructions for making a specific protein that triggers a desired immune response. If you imagine the DNA a little bit like a set of blueprints: once they’re inside the cell, it’s like someone’s handing an engineer detailed plans to construct a model version of the enemy. The immune system then learns to recognise this model, so it’s prepared for it if it encounters the real threat later. mRNA vaccines take an ever-so-slightly different approach. Instead of using DNA,…

“Scientists decide what trait they would like to introduce, such as resistance to drought” Summary GMOs are created using gene manipulation technology. By inserting a foreign gene into a new host, scientists can produce an organism that expresses a trait it wouldn’t usually have in nature.…

Genetically modified (GM) plants have been produced since the early 1980s, with the first run of GM tomatoes hitting the shelves in 1994 in the US. In a nutshell, GM foods have been genetically modified by inserting a new chain of genetic information that plays a particular function from one organism to another. Scientists take the natural pest control abilities or disease resistance of one plant and put the part of the DNA that provides that ability into another plant. Selecting desirable genetic traits in food products has existed for thousands of years. During the mid-1800s, Austrian scientist Gregor Mendel discovered that, through selective breeding, he could breed different generations to exhibit desirable traits. This technique was applied to selectively breed plants to produce larger fruits, bigger yields and so…

How does GEiGS work? The core principle of GEiGS is that we map all these RNAi genes, through minimalistic gene editing, changing maybe five to a max of 20 nucleotides. We redirect [them] to seek and destroy like smart missiles. Smart missiles have coordinates and explosive powers, so GEiGS is about changing the coordinates and keeping the explosiveness. We redirect the seek recognition of this molecule from one target to any target of choice. For example, we take an RNAi gene and we now target a nematode gene instead of other genes. Now you can redirect these RNAi genes against other genes within the plant cell to fight against a virus, fungus or any other pests. How do RNAi molecules work against insect pests? Ten years ago, we thought that…

Genes define who we are. They are the basic unit of heredity, each containing a coded set of instructions to make a protein. Humans have an estimated 20,500 genes, varying in length from a few hundred to more than 2 million base pairs. They affect all aspects of our physiology, providing the code that determines our physical appearance, the biochemical reactions that occur inside our cells and even, many argue, our personalities. Every individual has two copies of every gene – one inherited from each parent. Within the population, there are several alleles of each gene – that is, different forms of the same code, with minor alterations in the sequence. These alleles perform the same underlying function, but it’s the subtle differences that make each of us unique. Inside…

“DNA is a treasure trove of information that we’re only just beginning to explore” DNA is one of the greatest inventions of the natural world. It’s a chemical library, capable of storing vast quantities of data for billions of years. Passed from one generation of flora and fauna to the next, this microscopic structure is the engine of evolution. Every living creature uses DNA as its instruction manual. The genes contained within it instruct cells how to make the proteins they need to survive, grow and reproduce. DNA also records history, tracing the path evolution has taken to create the plants and animals we see today. Unlocking the secrets of DNA not only allows us to read our own life stories but also gives us the ability to predict –…

Archaeology Rebuilding history Skeletal remains can contain traces of ancient DNA for thousands of years. Extracting and sequencing this genetic material can reveal not only the sex of the individual but also their ethnicity. This can help to retrace the steps taken by our ancestors as they spread across the world. Forensics Solving crimes Forensic scientists identify DNA by examining sequences called ‘short tandem repeats’. These sequences occur in the gaps between genes and contain three or four DNA letters, repeated a different number of times in different people. Scientists count the number of repeats and compare them to repeats in a suspect’s DNA. Paternity Identifying fathers Children inherit half of their genes from their mother and half from their father. In a paternity test, scientists compare around 15 genes…

The process of fertilisation and embryo implantation is a wonderfully elegant yet complex process. This complexity, however, presents numerous opportunities for natural obstacles and barriers that prevent natural conception. Such obstacles include damage or blockage of the fallopian tubes, which can prevent the sperm and egg from meeting or the fertilised egg from reaching the uterus. Other disorders affect the release of eggs from the ovaries, and others affect males by reducing sperm number and activity. These challenges have driven the development of in vitro fertilisation (IVF), which offers a human-made bridge to pregnancy when the natural path is blocked. IVF is a process whereby the act of fertilisation, initial embryo division and implantation are conducted in the laboratory under the guidance of scientists. The world’s first ‘test tube’ baby…

A fertilised embryo that nestles into the uterine wall holds mammoth amounts of potential. The cells destined to become a foetus at that moment all look alike and number in the mere hundreds. Yet the organism that will arise from this small enclave will one day boast trillions of cells and be composed of a plethora of specialist cell types. How can the multitude of different cell types that make up our eyes, brain, lungs and skin come from such a small number of similar cells? The answer to this exponential increase in complexity and specialisation comes from stem cells. Every cell in the human body contains all the genetic information needed to perform any role. But for our bodies to develop and function efficiently, we need skin cells to behave…

Ageing is a fact of life we can’t escape no matter how hard we try; though, as a species, we’re getting better at prolonging the process. For the first time in human history, the global average life expectancy is above 70 years old. In comparison, back in 1950, the global average was 45 years old. We can predominantly thank the advancement of medicine for letting us live longer, but at what point do we stop growing and start ageing? It’s generally understood that once we surpass sexual maturity in our late 20s we make the transition from developing into ageing, also referred to as senescence, which means ‘the process of growing old’. After sexual maturity, our bodies become less efficient at dealing with physical stress and maintaining biological systems. That…

One way in which you could give yourself the opportunity to live even after death is with cryonic suspension. It may have been able to bring back Austin Powers after 30 years of suspension, but beyond the world of science fiction, the practicalities of cryonics remain a mystery. Right now we have the technology to cryogenically preserve a human body, but remain clueless on how to revive them when the time is right. It’s the belief that humankind will one day find a way to successfully thaw patients and treat whatever illnesses led to their death. The world leader in cryonics, Alcor, currently has 181 patients and has been storing humans for 49 years, including the company’s founder, Fred Chamberlain. The process of preserving a human body through cryonics involves…

Slow loris and cobra These furry tree climbers are surprisingly similar to snakes and have evolved to mimic some of their notable traits. The slow loris is one of the only known mammal species to produce venom for defence, which it secretes from a gland in its elbow and then licks to create a venomous saliva in its mouth that coats its teeth. When threatened, the slow loris hisses and will cross its arms over its head, making its face, complete with large eyes, resemble the shape and markings of a cobra. Wasps inside figs Figs produced by the fig tree (Ficus carica) are known as an inflorescence, not a fruit, where the inside of its bulbous body is full of clusters of small flowers and seeds. With its flowers…

Evolution usually happens over millions of years, so we can’t hope to see anything as dramatic as dinosaurs evolving into birds. The trouble with tracking evolution is that genetic changes must be passed on for generations before the effects become obvious. If animals live a long time, it’s hard to watch them evolve before our eyes. But that doesn’t mean we can’t see evolution happening in real time. During the Industrial Revolution, Britain went through a rapid period of environmental change. Factories churned out soot, coating the trees. Peppered moths had previously used birch trees for camouflage, and it was an advantage to be pale because dark moths stood out against the bark and were quickly spotted and eaten by birds. But, once the soot came, being darker became an advantage.…

Random mutations of genes can make some individuals slightly different to others, creating genetic variation. Predators, competition and other environmental factors can pressure organisms, and those with the most useful adaptations are more likely to survive and breed, passing on their genes to their offspring. This process, called natural selection, is what Darwin is famous for describing but it isn’t the only way evolution can occur. Another mechanism is called genetic drift. Here, rather than traits being selected for, they are lost or become more common due to a random event. This can happen if populations become separated, or if some individuals are killed, particularly if the population size is small. Genetic drift This analogy demonstrates how bottleneck events can change the course of evolution without any natural selection…

Your genes make you who you are. They’re inherited from your parents, and theirs from their parents before them, going all the way back to the time humans first emerged. Along the way, they’ve picked up traits that help us survive as a species, diversifying for humans living in different parts of the world with distinct needs and evolving along with the environments around us. Much of this is encoded as natural instinct. When a baby is born, it doesn’t need to be taught how to breathe or cry when it needs attention – this is hard-wired into our DNA. We know that when we’re tired we need to sleep and when we’re hungry we need to eat. The same goes for animals. Within two hours of being born, a…

MRSA Staphylococcus aureus As single-celled organisms, each time bacteria create a copy of themselves through cellular division, they run the risk of mutation. In 20 minutes or less, bacteria can double their population. When a mutation occurs, it quickly becomes the norm, such as in methicillin-resistant Staphylococcus aureus (MRSA): mutations have given it the ability to resist the effects of antibiotics. European house mouse Mus musculus Warfarin is a blood thinner used in pest control. The poison works by reducing vitamin K production, which helps the body form blood clots – an important process that prevents excess bleeding. A mutation in a gene called VKORC1 allows certain mice to produce more vitamin K and combat the blood-thinning ability of warfarin. Table coral Acropora Warming temperatures cause coral species to ‘bleach’, where…

“Viruses simply hijack other cells and turn them into virus factories” Are viruses alive? This is still a topic of debate among scientists. Viruses do not fit into our definitions of life, but they share some ‘life-like’ characteristics ALIVE “Viruses use the same molecular building blocks as other living organisms: RNA, DNA and protein” “Lots of other parasitic organisms depend on others for survival and cannot exist on their own” “Viruses evolve and have made complex changes to their genetics to adapt to their unique environments” DEAD “Viruses have a protective protein coat, but they do not have a membrane and are not cells” “Viruses cannot copy their own genetic code – they need living cells to do it for them” “Viruses don’t use any energy when they’re floating between…

Live-attenuated vaccines These use a weakened but still ‘live’ form of the pathogen or virus to stimulate an immune response without actually causing the disease. These vaccines closely mimic natural infections, generally providing strong, long‑lasting immunity. They require very careful handling and may not suit immunocompromised people. Examples Measles, mumps, rubella (MMR) and the famous oral polio vaccine. Toxoid vaccines These vaccines rely on toxins created from inactivated bacteria, which means the toxins can’t cause the actual disease itself. These vaccinations help the immune system identify and fight the poisons present during an illness. Booster doses are sometimes necessary to maintain long-term protection, and they are safe and effective. Examples The two biggest toxoid vaccines out there are those used to fight diphtheria and tetanus. Inactivated vaccines Inactivated vaccines are…

Microbes are extremely versatile microscopic organisms that include bacteria and viruses. Unseen by the naked eye, they conduct chemical conversions on a tiny scale, keeping the planet alive by recycling nutrients, both causing and preventing disease, but generally playing a vital role in our living planet. Some thrive in extreme environments, while others are carried with us at all times. There are 39 trillion microbial cells covering your body, maintaining your immune system and daily processes such as digestion. As small organisms, microbes have simple genetic structures, making them easier for scientists to study. By gaining a more thorough understanding of what different sections of DNA control within a microbe, scientists can alter them to favour certain traits. These are genetically engineered microbes – dubbed ‘designer microbes’. Microbes grow rapidly…

What if there were two of you? You could finish your chores and errands in half the time, juggle those overlapping social engagements or let one of you work while the other takes a mini vacation. In theory, the idea of cloning ourselves might seem like a no-brainer, but in actuality, creating human clones is rife with brain‑stretching scientific and moral obstacles. Since the creation of Dolly the sheep, the first cloned mammal, the last 20 years have been filled with many examples of DNA being taken from different species of animals, such as rabbits, rats, dogs and horses, and successfully creating a copy. Although the science works for those species, it’s not a one‑size-fits-all technique. One of the main challenges in human reproductive cloning is replicating our life span.…

The Human Genome Project The Human Genome Project, an initiative to map the sequence of the entire human genetic code, began in 1990 and was completed in 2003. The 3.3-billion base pair sequence was broken into sections of around 150,000 base pairs in length, and the sequence for each was identified. These were then joined and used to map the information onto chromosomes to determine which genes were found on each – and in what order. The genome map (right) shows a human chromosome compared with other animals; the colours are a ‘heat map’ demonstrating areas where genetic information has been conserved through evolution (the more fragmented the pattern, the more differences there are in the genetic code).…

CRISPR stands for ‘Clustered Regularly Interspaced Short Palindromic Repeat’. The acronym describes sections of DNA that read the same forwards and backwards (palindromes). They occur in groups in some bacteria and archaea, forming part of their defence against viruses. When a virus invades, the bacterium cuts out a piece of its genetic code and slots it between two CRISPR sequences. It then makes copies of the CRISPR DNA and the viral DNA sandwiched between. The copies, made from RNA, are like DNA but exist as single strands instead of double helixes. This means that the unpaired bases are free to stick to any matching code that they find inside the cell. If the same virus attacks again, the RNA sticks to its genetic code. This is where the second part…

Deoxyribonucleic Acid (DNA) is a chemical library, storing vast quantities of data for billions of years. Passed from one generation to the next, this microscopic structure is the engine of evolution. Every living creature uses DNA as its instruction manual. The genes in DNA tell cells how to make the proteins they need to survive, grow and reproduce. It may be the most famous molecule in the world, but what goes on inside that double helix? At the heart are four chemicals called nucleotides. Each contains a pentagon-shaped sugar molecule, a structure called a phosphate group and a protein fragment called a base. The sugar and the phosphate group are the same for every nucleotide. They join together side by side to form the backbone of each DNA strand. Like…

When scientists sequenced the human genome, they expected to find hundreds of thousands of genes. As it turned out, we only have approximately 25,000, and most of the rest of our genetic code is ‘junk’. Or so we thought. Genes are sections of genetic code that carry the instructions to build proteins; effectively, they are the instruction manual for the human body. When cells want to make a protein, they make lots of temporary copies of its gene. These copies pass out of the cell nucleus and into molecular machines, which read the sequence and assemble the protein. For the cell to work properly, getting the timing right is crucial. When the cell wants to turn production off, it could simply stop making copies of the gene, but old copies…

“One key benefit of cloning is that it allows you to introduce specific traits over just one generation. A desired trait may be caused by a specific DNA change and only be naturally present in one breed of cattle and lacking in another. However, we can design clones so that they have attributes from both breeds. For example, horn growth in dairy cattle can be a danger to other animals and those that care for the animals. To induce a lack of horns through a genetic path, you’d usually need to go through multiple generations of breeding, but alternatively we can edit the gene in cells prior to cloning to get this trait immediately. This helps to improve animal welfare as we can avoid farming practices like the dehorning procedure, which…

5 Ways to keep your mind sharp 1 Exercise  Studies in that regular animals have found exercise increases the number of blood vessels that feed oxygen to your brain. It’s also been found that new nerve cells and the connections between them are increased, which improves your cognitive abilities. 2 Sleep Getting sleep a seven to eight hours of night has been found to consolidate memories more efficiently. Some studies have found that bad sleep increases proteins in the brain that contribute to impaired brain function. 3 Eat well Having a healthy diet will improve many aspects of your life, but studies have shown that those eating a Mediterranean-style diet filled with vegetables, nuts, fish and fruit are less likely to develop conditions such as Alzheimer’s. 4 Stay social Social interactions have…

If, like many people, you’re curious about where you come from, you’ll no doubt have been tempted to take a genealogy test at some point. These clever bits of technology can help you discover your ancestral roots and maybe even connect you with one or two long-lost relatives. By analysing your DNA, these tests provide fascinating insights into your ethnic background and can reveal the countries, areas and regions that your ancestors lived in going back hundreds – or even thousands – of years. Beyond uncovering your heritage with a genealogy test, you may even be able to learn about some inherited health traits you may have. It really is a fascinating way to explore your and your immediate family’s personal history and understand the journey that your ancestors went…

It’s tempting to imagine that there is a story behind every trait, but not everything is an adaptation. Much of what you see today happened by chance or as a side effect of something else. Others are just remnants of traits that used to be useful but are not needed any more. Evolution often involves trade-offs and compromises, and it is constrained by the adaptations that an organism already has. Chance mutations Many traits don’t have an obvious reason or advantage and aren’t an adaptation. For example, around 25 per cent of the human population are ‘supertasters’, with far more taste buds than others. Side effects Some traits are side effects of others. The colour of our blood isn’t an adaptation; instead, it is a side effect of the molecule…

Even Darwin had trouble imagining that eyes were the product of evolution – but if you take it step by step, it makes sense. At the simplest level, eyes are spots or patches of pigments that respond to sunlight. If these pigments are on a flat surface, they only sense light and dark, but if they become dipped down into pits, they can be used to tell which direction the light is coming from. Then, if these pits become a little deeper, and the opening starts to close over, it forms the equivalent of a pinhole camera, restricting the light coming in and producing actual images. If that pinhole then becomes covered by a layer of transparent cells, the pit can fill with fluid, allowing a lens to start to…

This one is hard to argue with, given that the word ‘theory’ is right there in its title, but the real problem is the word ‘just’. In science, there’s no such thing as ‘just’ a theory. In general conversation, the word ‘theory’ is used interchangeably with words like ‘hunch’, ‘speculation’ and ‘belief’. It’s a fuzzy way to indicate that you think something might be true, but you don’t have all of the evidence to back it up. This is not the case in science. A scientific theory is based on evidence. There are many well-established principles of science, including evolution, that are centred on theories – for instance, that Earth orbits the Sun and that living things are made of cells. They provide a comprehensive explanation of what we see and…

Every human alive today can trace their ancestry back to East Africa around 200,000 years ago – DNA from a single woman still exists in every one of our cells. At the time, the human population was tiny, and her descendants are the only ones still alive today. They spread across the continent 100,000 years ago before radiating out in waves across the world. Scientists know the mother of humanity as mitochondrial Eve. We may have dispersed, but the genetic differences between us are surprisingly small. There is no major distinction between people living on different continents or people of different races. In fact, there are more genetic differences between subspecies of chimpanzee. This similarity makes people question whether we’ve stopped evolving completely. Evolution relies on a few key ingredients.…

As mammals, cats and dogs share a lot of similarities. They’re both warm-blooded, air-breathing, fur-covered creatures with almost the same organs. However, there are some differences in their physiology. For example, their brains are set up slightly differently from one another. Typically, a dog has a bigger brain than a cat, and a larger portion of its mass is dedicated to the cerebral cortex. This part of the brain is responsible for receiving and processing sensory information – the smells, sights and sounds a dog encounters – along with decision-making and social interaction. Cats have developed a brain that favours areas such as the hippocampus that are responsible for memory development, navigation and movement. Dogs have twice the number of neuron cells that transmit information around the brain than cats.…

Viruses specialise in getting past cellular defences to deliver genetic information into cells, but in nature, they often contain genes that cause disease. However, if we strip out these damaging stretches of code we could use the outer virus packaging to deliver useful genes to damaged cells. This is the idea behind viral vectors. The first step requires scientists to delete the parts of the viral genome that allow viruses to make copies of themselves. Then they add the code for different genes. When the modified virus infects a cell, it carries these new genes with it. The most commonly used viruses for vector science are adenoviruses and retroviruses. Adenoviruses have a DNA-based genome and temporarily infect mammalian cells. The cells make viral proteins for a short time and then…

We have a major problem. Since the dawn of humanity, we have been locked in a battle with microscopic organisms, and just when we thought we were starting to win, they’re fighting back. Bacteria cause some of the most devastating human diseases, from typhoid fever to tuberculosis, and until the 1920s we were utterly defenceless. But when Alexander Fleming ushered in the age of the antibiotic with his discovery of penicillin, we suddenly had a powerful weapon. Antibiotics work by stopping bacteria from dividing or by killing them outright. Thanks to them we can treat infections that were once fatal, we can perform complex surgery, and we can mass-produce food on an unprecedented scale. But we have used them and used them and used them, and the bacteria have started…

Chemotherapy The first chemotherapy drug was developed using mustard gas, a chemical weapon used during WWI. Scientists had noticed that the poison killed the fast-dividing cells of the bone marrow, so they adjusted the weapon to make nitrogen mustard, a treatment that could kill rapidly replicating cancer cells. Nitrogen mustard belongs to a group of drugs known as alkylating agents, which work by adding chemical units called alkyl groups to DNA. These interfere with the double helix structure, causing the genetic code to break apart. Other chemotherapies work in similar ways. Heavy metals cross-link DNA, preventing it from being read. Topoisomerase inhibitors stop the DNA helix from unwinding, and antimetabolites work by mimicking molecules involved in copying DNA, stopping the new sequence from being made. Anti-microtubule, or spindle poisons, stop…

To create a GMO, scientists must first decide what trait to introduce into an organism, such as resistance to drought or the ability to produce a particular vitamin. By analysing the genetic code, they can identify exactly which part of the DNA codes for the gene of interest and select enzymes that will cut out the part they need. Generally, they will then alter the genome of a plant by using a bacterium called Agrobacterium tumefaciens, which naturally enters plants’ cells in the wild. A few specific genes are then removed from the bacterial plasmid, a circular genetic structure that can replicate independently and be transmitted across bacteria. This cutting leaves a linear piece of DNA that codes just for replication instructions and for basic cell function. To create the…