Tag Archives: DNA

All our food is ‘genetically modified’ in some way – where do you draw the line?

The Conversation

James Borrell, Queen Mary University of London

In the past week you’ve probably eaten crops that wouldn’t exist in nature, or that have evolved extra genes to reach freakish sizes. You’ve probably eaten “cloned” food and you may have even eaten plants whose ancestors were once deliberately blasted with radiation. And you could have bought all this without leaving the “organic” section of your local supermarket.

Anti-GM dogma is obscuring the real debate over what level of genetic manipulation society deems acceptable. Genetically-modified food is often regarded as something you’re either for or against, with no real middle ground.

Yet it is misleading to consider GM technology a binary decision, and blanket bans like those in many European countries are only likely to further stifle debate. After all, very little of our food is truly “natural” and even the most basic crops are the result of some form of human manipulation.

Between organic foods and tobacco engineered to glow in the dark lie a broad spectrum of “modifications” worthy of consideration. All of these different technologies are sometimes lumped together under “GM”. But where would you draw the line?

1. (Un)natural selection

Think of carrots, corn or watermelons – all foods you might eat without much consideration. Yet when compared to their wild ancestors, even the “organic” varieties are almost unrecognisable.

Domestication generally involves selecting for beneficial traits, such as high yield. Over time, many generations of selection can substantially alter a plant’s genetic makeup. Man-made selection is capable of generating forms that are extremely unlikely to occur in nature.

Modern watermelons (right) look very different to their 17th-century ancestors (left). Christies/Prathyush Thomas, CC BY

2. Genome duplications

Unknowing selection by our ancestors also involved a genetic process we only discovered relatively recently. Whereas humans have half a set of chromosomes (structures that package and organise your genetic information) from each parent, some organisms can have two or more complete duplicate sets of chromosomes. This “polyploidy” is widespread in plants and often results in exaggerated traits such as fruit size, thought to be the result of multiple gene copies.

Without realising, many crops have been unintentionally bred to a higher level of ploidy (entirely naturally) as things like large fruit or vigorous growth are often desirable. Ginger and apples are triploid for example, while potatoes and cabbage are tetraploid. Some strawberry varieties are even octoploid, meaning they have eight sets of chromosomes compared to just two in humans.

3. Plant cloning

It’s a word that tends to conjure up some discomfort – no one really wants to eat “cloned” food. Yet asexual reproduction is the core strategy for many plants in nature, and farmers have utilised it for centuries to perfect their crops.

Once a plant with desirable characteristics is found – a particularly tasty and durable banana, for instance – cloning allows us to grow identical replicates. This could be entirely natural with a cutting or runner, or artificially-induced with plant hormones. Domestic bananas have long since lost the seeds that allowed their wild ancestors to reproduce – if you eat a banana today, you’re eating a clone.

Each banana plant is a genetic clone of a previous generation.
Ian Ransley, CC BY

4. Induced mutations

Selection – both human and natural – operates on genetic variation within a species. If a trait or characteristic never occurs, then it cannot be selected for. In order to generate greater variation for conventional breeding, scientists in the 1920s began to expose seeds to chemicals or radiation.

Unlike more modern GM technologies, this “mutational breeding” is largely untargeted and generates mutations at random. Most will be useless, but some will be desirable. More than 1,800 cultivars of crop and ornamental plants including varieties of wheat, rice, cotton and peanuts have been developed and released in more than 50 countries. Mutational breeding is credited for spurring the “green revolution” in the 20th century.

Many common foods such as red grapefruits and varieties of pasta wheat are a result of this approach and, surprisingly, these can still be sold as certified “organic”.

‘Golden Promise’, a mutant barley made with radiation, is used in
some premium whiskeys. 
Chetty Thomas/shutterstock

5. GM screening

GM technology doesn’t have to involve any direct manipulation of plants or species. It can be instead used to screen for traits such as disease susceptibility or to identify which “natural” cross is likely to produce the greatest yield or best outcome.

Genetic technology has allowed researchers to identify in advance which ash trees are likely to be susceptible to ash dieback disease, for instance. Future forests could be grown from these resistant trees. We might call this “genomics-informed” human selection.

6. Cisgenic and transgenic

This is what most people mean when they refer to genetically modified organisms (GMOs) – genes being artificially inserted into a different plant to improve yield, tolerance to heat or drought, to produce better drugs or even to add a vitamin. Under conventional breeding, such changes might take decades. Added genes provide a shortcut.

Cisgenic simply means the gene inserted (or moved, or duplicated) comes from the same or a very closely related species. Inserting genes from unrelated species (transgenic) is substantially more challenging – this is the only technique in our spectrum of GM technology that can produce an organism that could not occur naturally. Yet the case for it might still be compelling.

Campaigns like these are aimed at cis- and transgenic crops. But what about the other forms of GM food? Alexis Baden-Mayer, CC BY

Since the 1990s several crops have been engineered with a gene from the soil bacteria Bacillus thuringiensis. This bacteria gives “Bt corn” and other engineered crops resistance to certain pests, and acts as an appealing alternative to pesticide use.

This technology remains the most controversial as there are concerns that resistance genes could “escape” and jump to other species, or be unfit for human consumption. While unlikely – many fail safe approaches are designed to prevent this – it is of course possible.

Where do you stand?

All of these methods continue to be used. Even transgenic crops are now widely cultivated around the world, and have been for more than a decade. They are closely scrutinised and rightly so, but the promise of this technology means that it surely deserves improved scientific literacy among the public if it is to reach it’s full potential.

And let’s be clear, with global population set to hit nine billion by 2050 and the increasingly greater strain on the environment, GMOs have the potential to improve health, increase yields and reduce our impact. However uncomfortable they might make us, they deserve a sensible and informed debate.

The ConversationJames Borrell, PhD student in Conservation Genetics, Queen Mary University of London

This article was originally published on The Conversation. (Reblogged by permission). Read the original article.


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GM crops can benefit organic farmers too

The Conversation

Ian Godwin, The University of Queensland

Have you eaten organic food today? If you have eaten anything, then technically you’ve eaten organic. By definition, all food is organic, it just may not have been grown under industry standards, such as Australian Certified Organic (ACO).

Most people who choose to eat certified organic do so because they believe it is cleaner and greener, or chemical free. But the most modern cultivated plants are genetically modified organisms (GMOs) and so are precluded from being certified organic.

The Australian Organic organisation says that’s because there are no long-term studies on human health.

Prince Charles has warned that the cultivation of genetically modified (GM) crops is the biggest environmental disaster of all time.

The Australian Greens argue that:

[…] genetically modified foods have still not been proven safe […] Crop yields have not increased, but the use of pesticides on our food has. The only ones profiting from GM are the large GM companies.

But the research says different

Perhaps the Greens need to brush up on the science behind their claims. In the most comprehensive meta-analysis (of 147 publications) to date, researchers from Goettingen University have concluded that the adoption of GM technology has:

  • Reduced pesticide use by 37%
  • Increased crop yield by 22%
  • Increased farmer profits by 68%.

The yield and profit gains are considerably higher in developing countries than in developed countries, and 53% of GM crops are grown in developing countries.

A survey in the United States uncovered great difference in motivation among farmers who adopted GM herbicide-resistant soybean. Farmers like the no-till and low chemical use attributes. Even when it did not increase profitability, they enjoyed the increase in farm safety and particularly the safety of their families when using less herbicide with very low toxicity.

A similar study of the same soybeans in Argentina showed that total productivity increased by 10%, and more than half of the benefit had gone to the consumer.

In 2012, a joint Chinese-French study on GM cotton showed that insecticide usage more than halved, and the survival of beneficial insects had a positive impact on pest control. Since they adopted genetically modified Bt cotton, India has been producing twice as much cotton from the same land area with 65% less insecticide.

What do organic farmers really want?

Organic farmers really do care for their land and want to balance their impact on the land with producing healthier foods and improving the health of the soil.

But organic farms use more land and labour to produce the same amount of produce as conventional agriculture. That’s the major reason you pay more for organic products.

Organic farmers will maintain that if you can improve soil health, you can reduce the impact of pests and diseases. In fact, most farmers in Australia will say that, organic or not.

It works for some of the soil-borne problems but, not surprisingly, weeds really like healthy soils too. And fungal spores, plant-eating insects and aphids harbouring pathogenic viruses can and will travel a long way to get a piece of those healthy plants.

With all crop production, there is an element of biological warfare. No matter how hard any farmer tries, her crop will often need a little help to fight back.

All farmers use some ‘inputs’

So reluctantly, there will come a time when a farmer will have to use chemicals, or allowed “inputs” (remember that organic agriculture is chemical-free). They include things such as copper, rotenone, acetic acid, light petroleum derivatives, sodium chloride, boric acid and sulfur.

Different organic certifiers allow different “inputs”. Let’s use the case of the potato, which infamously succumbed to potato blight and precipitated the great Irish diaspora of the 19th century.

Potato blight is still around and organic potatoes succumb just like others, so farmers are allowed to apply copper sprays to control the fungus. After repeated applications, some soils accumulated toxic levels of copper, hence in 2001 the European Union (EU) and Australian organic certifiers limited application to 8kg/ha annually.

In 2006, the EU dropped this to 6kg/ha, and subsequently Germany and Switzerland cut further to 3-4kg/ha while Scandinavian countries banned the use of copper in agriculture, organic or conventional. Organic potato yields remain at 50% that of conventional yields.

In 2011, BASF launched a potato (Fortuna) that was totally resistant to potato late blight, and it could be cultivated without the need for fungicidal sprays, including copper. The potato contained two genes from a wild Mexican potato relative, and except for the fact that it was a GMO, it would be perfect as a clean and green organic potato crop.

Sadly, European agriculture rejected Fortuna potatoes.

Reduced emissions

There can be other benefits in GM crops, beyond yield and resistance. Rice produces 10% of the world’s methane emissions so imagine if somebody could reduce emissions by 90%, and make plants with larger seeds containing more energy.

Chuangxin Sun’s group at Swedish Agricultural University has done precisely that by transferring a single gene from barley to rice.

If all the world’s rice used this technology, it would be the equivalent of closing down 150 coal-fired power stations or removing 120 million cars from the road annually.

With many other plant scientists, I propose that the case-by-case scrutiny of GM crops would allow the organic industry to show it is willing to use the smartest technologies for improving the sustainable productivity of food and fibre production.

Many labs around the world, including those in my building, are full of bright young innovative scientists who want to make the world cleaner and greener.

We have GM crop plants with enhanced nutritional qualities, pest and disease resistance, larger grain sizes and the ability to produce more food with lower fertiliser inputs. Many of these plants have been modified with only a few DNA letters altered from the “wild” genes.

Adoption would massively improve the productivity of organic agriculture, and the productivity boost would help make organic food price competitive. So let’s talk about GM organics.

The ConversationIan Godwin, Professor in Plant Molecular Genetics, The University of Queensland

This article was originally published on The Conversation. (Reblogged by permission). Read the original article.


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Viruses don’t deserve their bad rap: they’re the unsung heroes you never see

The Conversation

Peter Pollard, Griffith University

The word “virus” strikes terror into the hearts of most people. It conjures up images of influenza, HIV, Yellow Fever, or Ebola. Of course we worry about these viruses—they bring us disease and sometimes an excruciatingly painful death.

But the 21 viral types that wreak havoc with the human body represent an insignificant fraction of the 100 million viral types on earth. Most viruses are actually vital to our very existence. No-one seems to stick up for the good guys that keep ecosystems diverse and balanced (although I did recently in a TEDx talk in Noosa).

The sheer number of these good viruses is astonishing. Their concentration in a productive lake or river is often 100 million per millilitre – that’s more than four times the population of Australia squeezed into a ¼ of a teaspoon of water.

Globally the oceans contain 1030 viruses. If you lined them all up they would extend for 10 million light years, or 100 times the distance across our galaxy. Collectively they would weigh as much as 75 million blue whales.

In short, there are a lot.

What are viruses?

Viruses are not living organisms. They are simply bits of genetic material (DNA or RNA) covered in protein, that behave like parasites. They attach to their target cell (the host), inject their genetic material, and replicate themselves using the host cells’ metabolic pathways, as you can see in the figure below. Then the new viruses break out of the cell — the cell explodes (lyses), releasing hundreds of viruses.

The viral cycle. Peter Pollard

Viruses are very picky about who they will infect. Each viral type has evolved to infect only one host species. Viruses that infect bacteria dominate our world. A virus that infects one species of bacteria won’t infect another bacterial species, and definitely can’t infect you. We have our own suite of a couple of dozen viral types that cause us disease and death.

A deadly dance

Algae and plants are primary producers, the foundation of the world’s ecosystems. Using sunlight they turn raw elements like carbon dioxide, nitrogen and phosphorus into organic matter. In turn, they are eaten by herbivores, which are in turn eaten by other animals, and so on. Energy and nutrients are passed on up the food chain until animals die. But what ensures that the primary producers get the raw elements they need to get started?

The answer hinges on the viruses’ relationship with bacteria.

A virus doesn’t go hunting for its prey. It relies on randomly encountering a host — it’s a numbers game. When the host, such as a bacterial cell, grows rapidly, that number increases. The more of a bacterial species there is, the more likely it will come into contact with its viral nemesis — “killing the winner”. This means that no single bacterial species dominates an ecosystem for very long.

In freshwater, for example, you see very high rates of bacterial growth. You would think this high bacterial production would become part of the food chain and end up as fish food. But that is rarely the case.

We now realise that the bacteria actually disappear from these ecosystems. So where do the bacteria go?

The answer lies in the interaction of the bacteria and viruses. When a virus bursts open a bacterial cell its “guts” are spewed back into the water along with all the new viruses. The cell contents then become food for the neighbouring bacteria, thereby stimulating their growth. These bacteria increase in numbers and upon coming into contact with their viral nemesis they, too, become infected and lyse.

Viruses make the world go ‘round

This process of viral infection, lysis, and nutrient release occurs over and over again. Bacteria are, in effect, cannibalising each other with the help of their associated viruses. Very quickly, the elements that support the food web are put back into circulation with the help of viruses, as you can see in the graphic below.

How nutrients are recycled. Peter Pollard

This interaction ensures inorganic nutrients are readily available to algae and plants on which ecosystems depend. It’s the combination of high bacterial growth and viral infection that keeps ecosystems functioning. This explains why we don’t see bacteria in food webs. Viruses short circuit bacterial production passing higher up the food chain so it doesn’t become fish food in freshwater ecosystems.

Most of the food (dissolved organic carbon) that drives the very high bacterial growth in freshwater comes from the terrestrial environment. Indeed, freshwater viral/bacterial interactions appear to be a critical link in carbon cycle between the land and atmosphere.

Soil viral ecology studies lag way behind water research. Viral dynamics in terrestrial ecosystems are complicated as soils can bind and inactivate viruses to limit their ability to infect other organisms. We may well be relying on freshwater processes to complete the global carbon cycle, as shown in the graphic above.

In freshwater, viruses are enhancing the rate of bacterial decomposition whereby complex organic matter is quickly and efficiently mineralised into their simple inorganic components such as carbon dioxide, nitrogen, and phosphorus.

Thus viruses are a critical part of inorganic nutrient recycling. So while they are tiny and seem insignificant, viruses actually play an essential global role in the recycling of nutrients through food webs. We are only just now beginning to appreciate the extent of their positive impact on our survival.

One thing is for sure, viruses are our smallest unsung heroes.

The ConversationPeter Pollard, Associate Professor, Griffith University

This article was originally published on The Conversation. (Reblogged by permission). Read the original article.

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Why the causes of cancer are more than just random bad luck

The Conversation

By Darren Saunders, Garvan Institute

What causes cancer? This deceptively simple question has a devilishly complex answer. So when US researchers proposed a relatively simple mathematical formula to explain a long-standing conundrum in cancer earlier this year, it was bound to get a lot of attention.

The study published in the journal Science suggested a correlation between the variation in cancer occurrence between different tissues and the number of stem cell divisions in each tissue. In other words, it said the tissues most vulnerable to cancer are those with the greatest number of stem cell divisions.

Most of the reporting about the research ran with the line that “cancer is all down to bad luck”, implying that developing the disease is out of our hands and that preventative efforts might be useless. But is that really the case?

Much of the misunderstanding seems to have arisen from the authors’ statement that a third of the variation in cancer risk among tissues is attributable to environmental or inherited factors, with the majority due to random mutations during DNA replication in normal cells. This statement about relative risk was overblown into blanket conclusions about the underlying causes of cancer.

The wonder of replication

Cancer emerges when one of the cells that make up your tissues (and organs) grows and divides without control, losing its specialised function and invading other tissue. This happens when normal control of cell growth and division is compromised through changes, or mutations, in your genome (the chemical instruction book for life).

Mutations lie at the heart of cancer biology.

The genome is made from a chemical alphabet of just four letters (A,T,G, and C) “written” into DNA. It works like a kind of computer software for our cells, with strict instructions for growth and function.

Each of the 100 trillion cells in your body contains roughly six billion letters (called nucleotides) of this code, condensed into a thin strand of DNA about two metres long. To put this into perspective, if you stretched out all the DNA in a human body it would reach around the moon and back several times.

Every time a cell divides, the genome must be copied accurately and quickly. This synthesis of new DNA is called replication, and the numbers behind it are staggering. UK researcher John Diffley has calculated that you will have synthesised the equivalent of a light-year of DNA (10 trillion kilometres) by the time you’re 50.

Words simply cannot do this amazing process justice, but this short video by award-winning animator Drew Berry will blow your mind:


DNA replication has evolved to be incredibly efficient and reliable, but random mistakes (mutations) occasionally happen. Still, they occur at a rate of less than once per genome per cell division, thanks to some impressive molecular proofreading machines, which constantly survey the newly copied DNA and correct errors.

But with so many cells dividing so often, DNA replication still represents a major source of mutations. And every cell division increases the chance of accumulating mutations in important genes, increasing the likelihood of cancer.

Other sources of mutation

Mutations can take many forms and can emerge in a number of ways – not just through replication errors. We inherit between 50 and 100 mutations from our parents at birth, for instance, and any new or de novo mutations act on this inherited genetic background.

Even normal cellular metabolism damages DNA through the production of reactive oxygen. And, in a sinister twist, many of the inherited mutations that predispose people to cancer hit genes that control the DNA proofreading and repair systems (such as the breast cancer genes BRCA1 and BRCA2). This has the effect of amplifying the rate of new mutations.

The other major causes of DNA mutation are lifestyle or environmental factors. We are exposed to a range of these in our everyday lives, such as UV radiation from sunshine, and chemicals including asbestos or from smoking cigarettes.

Lifestyle factors including diet and alcohol consumption may also contribute. Some viruses and bacteria are known to cause DNA damage leading to cancer. They include the human papillomavirus (HPV) for cervical cancer and H. pylori for gastric cancer.

Not off the hook: alcohol and diet can contribute to DNA mutations. Source: Erik/Flickr, CC BY-NC

Although these different agents leave unique chemical signatures in the DNA, they are still essentially random events. Random mutations are, in fact, the raw material driving evolution. And the processes of mutation and evolution are accelerated in cancer. Indeed, we are only now starting to understand the importance of evolution in driving cancer emergence and spread, as well as its resistance to therapy.

Minimising risk

Where does this leave the idea that cancer is all down to bad luck? Is modifying your lifestyle to minimise exposure to risk factors futile?

As usual, reality lies somewhere in the middle of competing narratives. Life is a kind of genetic gamble. We have to play the cards dealt us, but we can stack the odds in either direction by altering our exposure to environmental and lifestyle factors. Suggesting cancer is all down to bad luck dilutes the important message that risk can be modified by behaviour.

The cancer lexicon is littered with notions of guilt and blame. Death is often framed as “losing the battle with cancer”, for instance. And patients and their families are bombarded by gurus profiteering from various diet and lifestyle interventions. Their implicit messages can often leave people feeling that their cancer is all their own fault and wondering if there was something they could have done differently.

The fact remains that, in many cases, there isn’t.

The ConversationThis article was originally published on The Conversation. (Reblogged by permission). Read the original article.


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Bird tree of life shows ‘explosive evolution’: studies

The Conversation

By Bryonie Scott, The Conversation and Tessa Evans, The Conversation

Today’s land birds, from ducks to eagles, shared a common ancestor after dinosaurs went extinct – just one finding from bird gene studies published in journals, including Science and GigaScience, today.

Genetic data of 48 bird species were sequenced in a massive international collaboration to create a new and detailed version of the avian tree of life.

“Birds have always been very good for this kind of work because we have a greater understanding about the world’s birds than we do about any of the other vertebrate groups,” Simon Griffith, Associate Professor of Avian Behavioural Ecology at Macquarie University, said.

“We are familiar with almost all the birds in the world – around 10,000 species – and we know how they differ, in important characteristics such as how long they live, how many offspring they have each year, how old they are when they breed.”

About 66 million years ago, a mass extinction event wiped out around 80% of Earth’s plant and animal population, but opened the door for the rapid expansion of birds.

Giant terror birds are similar to a common ancestor of all land birds. Marcelo Braga/Flickr, CC BY

Only a few bird lineages survived the mass extinction, and most modern land birds such as songbirds, owls and woodpeckers share a common apex predator ancestor.

This top-of-the-food-chain brute was similar to the giant terror birds which stalked the Americas between 27 million and 15,000 years ago.

“The main problem in resolving the relationships among birds is that they diversified very quickly,” Research Director and the Curator of the Australian National Wildlife Collection, CSIRO, Leo Joseph said.

Extreme adaptations

Birds are among the most widespread land animals and have experienced evolutionary adaptations to extreme environments. Penguins live in some of the harshest conditions on Earth, and DNA analysis, published in GigaScience, confirmed fossil evidence that penguins first appeared in Antarctica around 60 million years ago.

“If you have a complete genome, you can compare the variations between the chromosomes and get a picture of the population history” Sankar Subramanian, a research fellow at Griffith University and who worked on the project, said.

“By comparing the complete genome of penguins living today we can track when evolutionary changes occurred, up to 200,000 years ago.”

This aspect of the research, Emperor penguins were found to have a stable population, but Adélie penguins present a very different story, showing fluctuations in population matching extreme climactic periods.

In a warmer period 150,000 years ago there was a large population explosion, but in a more recent glacial period the population declined dramatically.

Adélie penguins struggle in glacial periods as they require ice-free land for nesting. Dominique Génin/Flickr, CC BY-NC-ND

Rather than being evolutionary in origin, Dr Subramanian explained the fluctuations depended on “how much ice-free land is available for nesting and breeding”.

Compared to other bird species, penguins had more genes for lipid metabolism, which is essential for forming layers of blubber to withstand the cold.

This subgroup of the project hopes to look at penguins which live in tropical and temperate waters such as the Galápagos Islands and New Zealand to see how more recent evolutionary adaptations have affected genes of modern penguins.

Now that these hallmark studies have been completed, and the bird tree of life established with some degree of authority, it provides a scaffold for further research.

“This new study helps tease apart the rapid diversification of birds, which has been a long-standing problem,” Dr Joseph said.

“We can now address really interesting questions,” Associate Professor Griffith said. “When did song learning evolve? When did birds evolve different patterns of parental care?”

These insights provide sought-after answers about how species can diversify so quickly to fill the ecological niches.

This articled was edited on Friday December 12, 2014, to clarify some quotes by Dr Leo Joseph.

The ConversationThis article was originally published on The Conversation. (Republished with permission). Read the original article.

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DNA and GM foods

by Tim Harding B.Sc

(An edited version of this essay was published in The Skeptic magazine, September 2014, Vol 34 No 3, under the title ‘The Good Oil’.  The essay is based on a talk presented to the Mordi Skeptics, Tuesday 5 April 2011; and later to the Sydney Skepticamp, 30th April 2011.)

In May 2014, a farmer accused of ‘contaminating’ his neighbour’s land with genetically modified canola won a highly publicised civil case in the Western Australian Supreme Court (Marsh v. Baxter, 2014).  Although the case was about a claim of conflicting land use rather than food safety, it fired up the long-running community debate about genetically modified foods in Australia.  It also exposed a lot of misinformation and misunderstanding about DNA and genetic modification.

This essay discusses the nature and structure of DNA; together with the history of its discovery. It makes the point that artificial selection been occurring since the dawn of civilisation; and that the outcome of different methods of artificial selection is the same – modification of the genetic code by human intervention. Not only is there no evidence that genetically modified foods are unsafe to eat, but there is no mechanism by which they could be unsafe.

Brief history of DNA research

The rules of genetics were largely understood since Gregor Mendel’s ‘wrinkled pea’ experiments in the 1860s but the mechanisms of inheritance remained a mystery.   Charles Darwin knew in the 1850s there must have been such a mechanism (but his later speculations about it – called pangenesis – were wrong).[1]  The units of inheritance were called genes, but it was not understood where genes were located in the body or what they physically consisted of.

After the rediscovery of Mendel’s work in the 1890s, scientists tried to determine which molecules in the cell were responsible for inheritance.  In 1910, Thomas Hunt Morgan argued that genes are on chromosomes, based on observations of a sex-linked white eye mutation in fruit flies.  In 1913, his student Alfred Sturtevant used the phenomenon of genetic linkage to show that genes are arranged linearly on the chromosome.  It was soon discovered that chromosomes consisted of DNA and proteins, but DNA was not identified as the gene carrier until 1944.

Watson and Crick’s breakthrough discovery of the chemical structure of DNA in 1953 finally revealed how genetic instructions are stored inside organisms and passed from generation to generation.[2]  In the following years, scientists tried to understand how DNA controls the process of protein production. It was discovered that the cell uses DNA as a template to create matching messenger RNA (a single-strand molecule with nucleotides, very similar to DNA). The nucleotide sequence of a messenger RNA is used to create an amino acid sequence in protein; this translation between nucleotide and amino acid sequences is known as the genetic code.

DNA structure

The molecular basis for genes is deoxyribonucleic acid (DNA) a double-stranded molecule, coiled into the shape of a double-helix.  DNA is composed of twin backbones of sugars and phosphate groups joined by ester bonds.  These backbones hold together a chain of nucleotides, of which there are four types: adenine (A), cytosine (C), guanine (G), and thymine (T).  Genetic information in all living things exists in the sequence of these nucleotides, and genes exist as stretches of sequence along the DNA chain.[3]  Each nucleotide in DNA preferentially pairs with its partner nucleotide on the opposite strand: A pairs with T, and C pairs with G using weak hydrogen bonds.  Thus, in its two-stranded form, each strand effectively contains all necessary information, redundant with its anti-parallel partner strand.  This structure of DNA is the physical basis for inheritance: DNA replication duplicates the genetic information by enzymes splitting the strands (like a zipper) and using each strand as a template for synthesis of a new partner strand.

Chemical structure of DNA (Source: Wikimedia Commons)

Chemical structure of DNA (Source: Wikimedia Commons)

The sequence of these nucleotides A, C, G and T is a code, similar to the binary digital code used in computing.  When you consider that all the instructions for everything that computers can produce: text, calculations, music and images is stored as a binary sequence of ones and zeros, it is not hard to conceive how the instructions for making and operating living organisms can be stored as a four letter code.

Genes are arranged linearly along very long chains of DNA sequence, which comprise the chromosomes.  In bacteria, each cell usually contains a single circular chromosome, while eukaryotic organisms (including plants and animals) have their DNA arranged in multiple linear chromosomes.  These DNA strands are often extremely long; the largest human chromosome (No. 1), for example, is about 247 million base pairs in length. The full set of hereditary material in an organism (usually the combined DNA sequences of all 46 chromosomes in humans) is called the genome (approx. 3 billion base pairs in humans).

The genetic code is the set of rules by which information encoded in genetic material (DNA or mRNA sequences) is translated into proteins (amino acid sequences) by living cells.  The code defines a mapping between tri-nucleotide sequences, called codons, and amino acids. With some exceptions, a triplet codon in a nucleic acid sequence specifies a single amino acid.[4]

Translation of genetic code into proteins (Source: Wikimedia Commons)

Translation of genetic code into proteins (Source: Wikimedia Commons)

However, the human genome contains only ca. 23,000 protein-coding genes, far fewer than had been expected before its sequencing.  In fact, only about 1.5% of the genome codes for proteins, while the rest consists of non-coding RNA genes, regulatory sequences, introns, and noncoding DNA (once known as ‘junk DNA’). Genetic recombination during sexual reproduction involves the breaking and rejoining of two chromosomes (one from each parent) to produce two new rearranged chromosomes, thus providing genetic diversity and increasing the efficiency of natural selection.

Genetic modification

One of the biggest public misunderstandings is about the very term ‘genetic modification’.  Genes can be modified in 2 main ways:

Artificial selection can occur in 4 main ways:

  • traditional plant and animal breeding (long-term);
  • mutagenesis (random exposure to chemical or radiological mutagens);
  • RNA interference (switching genes on or off);
  • genetic engineering (short-term) – the targeted insertion or deletion of genes in the laboratory (which cannot easily be achieved by other methods).

The end result of the different methods of artificial selection is the same – modification of the genetic code by human intervention.  All DNA, whether modified naturally or artificially, is biochemically and nutritionally the same.  The only difference is in the genetic code, that is, the sequence of the bases G, C, T and A.  In other words, DNA is DNA – there are no such thing as ‘natural DNA’ and ‘artificial DNA’.

They are all ways of artificially modifying genes, yet for some illogical reason plant and animal breeding is not usually referred to in the media as genetic modification – possibly because it started a long time (c. 11,000 years ago) before genetics was understood.  However, to avoid any confusion, in this paper I will refer to genetic modification of foods by genetic engineering as genetically engineered foods (GE foods).

As a result of artificial selection, all farmed foods we eat today have been genetically modified by humans via plant and animal breeding.  This includes all meats except for wild game and kangaroo; and most farmed fish such as salmon.

Similarly all plants we eat (vegetables, fruits,  nuts, herbs and spices) have been genetically modified by humans.  Many varieties bear little resemblance to their original wild forms.  A wheat grain is a genetically modified grass seed.  Can anybody think of a plant food that has not been modified by humans?  (The only ones any of us at the meetup could think of were bush tucker, which is rarely found in Australian shops or supermarkets.  Seaweed was later suggested at the Sydney Skepticamp).

Whenever we eat and digest proteinaceous food, the DNA inside the food gets broken down into single nucleotides before absorption in the small intestine, destroying the genetic code anyway.  It is therefore logically impossible for any changes in the genetic code, whether artificial or natural, to make DNA unsafe to eat.

Not only is it logically impossible, but there is no empirical evidence that genetically modified foods are harmful.  The technology to produce genetically engineered (GE) plants is now over 30 years old, yet in all that time there has not been a single instance of anybody becoming ill, let alone dying, as a result of eating GE foods.

In a recent major review of the scientific literature on last 10 years of the world’s GE crop safety research, the reviewers conclude that ‘the scientific research conducted so far has not detected any significant hazard directly connected with the use of GE crops’.  The authors further believe that ‘genetic engineering and GE crops should be considered important options in the efforts towards sustainable agricultural production’ (Nicolia et al, 2013).

GE foods

GE foods can be produced by either cisgenesis (within the same species) or transgenesis (from different species).[5]  However, the point needs to be made that the human genome naturally contains genes resulting from billions of years of evolution – even genes from our fishy ancestors.  A substantial fraction of human genes seem to be shared among most known vertebrates.  For example, the published chimpanzee genome differs from that of the human genome by 1.23% in direct sequence comparisons.  We also share many genes with plants.

“The real question here is not whether there is a GMO tomato with a fish gene, but who cares? It’s not as if eating fish genes is inherently risky—people eat actual fish. Furthermore, by some estimates people share about 70 percent of their genes with fish. You have fish genes, and every plant you have ever eaten has fish genes; get over it.”[6]

GE foods were first put on the market in the early 1990s.  Typically, genetically modified foods are transgenic plant products: soybean, corn, canola, and cotton seed oil.  

GE genes may be present in whole foods, such as wheat, soybeans, maize and tomatoes.  The first commercially grown genetically modified whole food crop was a tomato (called FlavrSavr), which was modified to ripen without softening, in 1994.  These GE whole foods are not presently available in Australia.  GE food ingredients are, however, present in some Australian foods.  For example, soy flour in bread may have come from imported GE soybeans.[7]

In addition, various genetically engineered micro-organisms are routinely used as sources of enzymes for the manufacture of a variety of processed foods. These include alpha-amylase from bacteria, which converts starch to simple sugars, chymosin from bacteria or fungi that clots milk protein for cheese making, and pectinesterase from fungi which improves fruit juice clarity.


Genetic engineering can also be used to increase the amount of particular nutrients (like vitamins) in food crops. Research into this technique, sometimes called ‘nutritional enhancement’, is now at an advanced stage. For example, GE golden rice is an example of a white rice crop that has had the vitamin A gene from a daffodil plant inserted. This changes the colour and the vitamin level for countries where vitamin A deficiency is prevalent. Researchers are especially looking at major health problems like iron deficiency. The removal of the proteins that cause allergies from nuts (such as peanuts and Brazil nuts) is also being researched.[8]

Animal products have also been developed, although as of July 2010 none are currently on the market.  However, human insulin has been produced using GE E.coli bacteria since 1978.  In 2006 a pig was controversially engineered to produce omega-3 fatty acids through the expression of a roundworm gene.  Researchers have also developed a genetically-modified breed of pigs that are able to absorb plant phosphorus more efficiently, and as a consequence the phosphorus content of their manure is reduced by as much as 60%.

Once again, there is no evidence of any person being harmed by eating genetically engineered foods.  The reasons why genetically engineered whole foods are not yet available in Australia are political or emotional rather than scientific.

Benefits of GE foods

There is a need to produce inexpensive, safe and nutritious foods to help feed the world’s growing population. Genetic engineering may provide:

  • Sturdy plants able to withstand weather extremes (such drought);
  • Better quality food crops;
  • Higher nutritional yields in crops;
  • Inexpensive and nutritious food, like carrots with more antioxidants;
  • Foods with a greater shelf life, like tomatoes that taste better and last longer;
  • Food with medicinal (nutraceutical) benefits, such as edible vaccines – for example, bananas with bacterial or rotavirus antigens;
  • Crops resistant to disease and insects and produce that requires less chemical application, such as pesticide and herbicide resistant plants: for example, GE canola.[8]

Objections to GE foods

So why is there such significant opposition to GE foods from some vocal lobby groups? Critics have objected to GE foods on several grounds, including:

  • the appeal to nature fallacy (natural products are good and artificial products are bad);
  • alleged but unproven safety issues, (there is no evidence of any adverse health effects, including allergies, in the 20 years since GE foods became available);
  • marketing concerns about ‘contamination’ of so-called organic food crops by GMOs (such as in the Marsh -v-Baxter case);
  • ecological concerns about the spread of GMOs in the wild, and
  • economic or ideological concerns raised by the fact that these organisms are subject to intellectual property rights usually held by big businesses.

The only one of these objections that may have any scientific legitimacy is the ecological concern about the spread of GMOs in the wild.  However, the use of GE technology is highly regulated by Australian governments and any such ecological concerns are fully taken into account.

Current food regulations in Australia state that a GE food will only be approved for sale if it is safe and is as nutritious as its conventional counterparts.  Food regulatory authorities require that GE foods receive individual pre-market safety assessments prior to use in foods for human consumption.  The principle of ‘substantial equivalence’ is also used.  This means that an existing food is compared with its genetically modified counterpart to find any differences between the existing food and the new product.  An important to note is that Australia has the most rigorous food safety testing regime in the world, and that GE foods are tested even more rigorously than non-GE foods. Because of this higher level of testing, GE foods are likely to be safer than non-GE foods.

Foods certified as organic or biodynamic should not contain any GE ingredients, according to voluntary organic food industry guidelines.

Here is a list of 114 peer-reviewed articles and meta reviews, mostly published in moderate to high impact factor journals that support the safety of GMO crops over a wide range of hypotheses.  The consensus position of the American Association for the Advancement of Sciences on GM foods is:

“Indeed, the science is quite clear: crop improvement by the modern molecular techniques of biotechnology is safe… The World Health Organization, the American Medical Association, the U.S. National Academy of Sciences, the British Royal Society, and every other respected organization that has examined the evidence has come to the same conclusion: consuming foods containing ingredients derived from GM crops is no riskier than consuming the same foods containing ingredients from crop plants modified by conventional plant improvement techniques.”


American Association for the Advancement Of Science (2012). Statement by the AAAS Board of Directors On Labeling of Genetically Modified Foods. 20 October 2012.

Better Health Channel (2011) Fact Sheet – Genetically modified foods www.betterhealth.vic.gov.au Melbourne: State of Victoria.

Darwin, Charles (1868),The Variation of Animals and Plants under Domestication (1st ed.), London: John Murray.

Lynas, Mark (29 April 2013) Time to call out the anti-GMO conspiracy theory.  Mark Lynas speech hosted by the International Programs – College of Agriculture and Life Sciences (50th Anniversary Celebration) , and the Atkinson Center for a Sustainable Future, Cornell University.

Marsh -v-Baxter [2014] WASC 187 (28 May 2014).

Nocolia, A., Mazo, A., Veronesi, F., and Rosellini (2013) ‘An overview of the last 10 years of the genetically engineered crop safety research’. Critical Reviews in Biotechnology. Informa Healthcare USA Inc. ISSN: 0738-8552 (print) 1549-7801 (electronic).

Skeptical Raptor’s Blog. What does science say about GMO’s–they’re safe. Updated 19 November 2014.

Novella, Stephen (2014) ‘No Health Risks from GMOs’. The Science of Medicine .Volume 38.4, July/August 2014.

Watson J.D. and Crick F.H.C. (1953) A Structure for Deoxyribose Nucleic Acid. Nature 171 (4356): 737–738.

Other information is from Wikipedia and the author’s knowledge as a former biochemist.  (According to convention, anonymous Wikipedia pages, whilst thought to be mostly factually correct, are not citable as references).

[1] Darwin, 1868.

[2] Watson and Crick, 1953.

[3] Viruses are the only exception to this rule—sometimes viruses use the very similar molecule RNA instead of DNA as their genetic material.

[4] Not all genetic information is stored using the genetic code. All organisms’ DNA contains regulatory sequences, intergenic segments, and chromosomal structural areas that can contribute greatly to phenotype by controlling how the genes are expressed.  Those elements operate under sets of rules that are distinct from the codon-to-amino acid paradigm underlying the genetic code.

[5] For example, the gene from a fish that lives in very cold seas has been inserted into a strawberry, allowing the fruit to be frost-tolerant.  However, this has not as yet been done for currently available commercial food crops.

[6] Novella, 2014.

[7] Better Health Channel, 2011.

[8] Better Health Channel, 2011.

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