Can Environment change your DNA?

 Can the Environment change your DNA?

What is DNA?

Deoxyribonucleic acid (abbreviated DNA) is the molecule that carries the genetic information for the development and functioning of an organism. DNA is made of two linked strands that wind around each other to resemble a twisted ladder — a shape known as a double helix. Each strand has a backbone made of alternating sugar (deoxyribose) and phosphate groups. Attached to each sugar is one of four bases: adenine (A), cytosine (C), guanine (G), or thymine (T). The two strands are connected by chemical bonds between the bases: adenine bonds with thymine, and cytosine bonds with guanine. The sequence of the bases along DNA’s backbone encodes biological information, such as the instructions for making a protein or RNA molecule.

Can DNA be changed by the environment?

While the sequence of DNA may not be affected by your environment, the way genes work—called gene expression—can. 

Think of DNA as a computer’s hardware; there may be several types of software programs that can regulate what the hardware does. Epigenetics is the study of heritable changes in gene expression that don’t involve changing the underlying DNA—effectively, software changes that cause alterations in gene function.

According to Duke Magazine, environmental factors such as food, drugs, or exposure to toxins can cause epigenetic changes by altering the way molecules bind to DNA or changing the structure of proteins that DNA wraps around. These structural changes can result in slight changes in gene activity; they also can produce more dramatic changes by switching genes on when they should be off or vice versa.

These changes are heritable, meaning they can be passed on from parent cell to daughter cell within the body, and from parent to child. An extraordinary study of survivors of the Dutch famine during World War II, for example, has shown that the effect of epigenetic changes caused by hunger doesn't show up in the survivors’ children, but they do in their children’s children. This perhaps suggests the adage should not merely be, “You are what you eat,” but also, “You are what your grandparents ate.”

What environmental factors affect DNA?

Our bodies are affected by several external environmental factors. Pollution tends to have the most obvious and severe negative effects, but other factors can affect our DNA and gene expression, which, in turn, affect our hormones and metabolic processes. According to Scitable, light and temperature can affect us as easily as drugs, food, and chemicals.

Light and Temperature

Temperature and light are external environmental factors that may influence gene expression in certain organisms. For example, Himalayan rabbits carry the C gene, which is required for the development of pigments in the fur, skin, and eyes, and whose expression is regulated by temperature. Specifically, the C gene is inactive above 35°C, and maximally active from 15°C to 25°C. This temperature regulation of gene expression produces rabbits with a distinctive coat coloring. The gene is inactive in the warm, central parts of the rabbit's body, and no pigments are produced, causing the fur color to be white. Meanwhile, in the rabbit's extremities (i.e., the ears, tip of the nose, and feet), where the temperature is much lower than 35°C, the C gene actively produces pigment, making these parts of the animal black.

Light can also influence gene expression, as in the case of butterfly wing development and growth. For example, in 1917, biologist Thomas Hunt Morgan conducted studies in which he placed Vanessa Urtica and Vanessa io caterpillars under red, green, or blue light, while other caterpillars were kept in the dark. When the caterpillars developed into butterflies, their wings showed dramatic differences. Exposure to red light resulted in intensely colored wings, while exposure to green light resulted in dusky wings. Blue light and darkness led to paler-colored wings. In addition, the V. Urtica butterflies reared under blue light, and V. io butterflies reared in the dark were larger than the other butterflies.

Drugs

The presence of drugs or chemicals in an organism's environment can also influence gene expression in the organism. Cyclops fish is a dramatic example of how an environmental chemical can affect development. In 1907, researcher C. R. Stockard created cyclopean fish embryos by placing fertilized Fundulus heteroclitus eggs in 100 mL of seawater mixed with approximately 6 g of magnesium chloride. Normally, F. heteroclitus embryos feature two eyes; however, in this experiment, half of the eggs placed in the magnesium chloride mixture gave rise to one-eyed embryos

 Food

One interesting aspect of thinking of food as a type of biological information is that it gives new meaning to the idea of a food chain. Indeed, if our bodies are influenced by what we have eaten – down to a molecular level – then what the food we consume “ate” also could affect our genome. For example, compared to milk from grass-fed cows, the milk from grain-fed cattle has different amounts and types of fatty acids and vitamins C and A. So when humans drink these different types of milk, their cells also receive different nutritional messages.

Similarly, a human mother’s diet changes the levels of fatty acids as well as vitamins such as B-6, B-12, and folate that are found in her breast milk. This could alter the type of nutritional messages reaching the baby’s own genetic switches, although whether or not this has an effect on the child’s development is, at the moment, unknown.

And, maybe unbeknownst to us, we too are part of this food chain. The food we eat doesn’t tinker with just the genetic switches in our cells, but also with those of the microorganisms living in our guts, skin, and mucosa. One striking example: In mice, the breakdown of short-chain fatty acids by gut bacteria alters the levels of serotonin, a brain chemical messenger that regulates mood, anxiety, and depression, among other processes.

Chemicals

An example of how chemical environments affect gene expression is the case of supplemental oxygen administration causing blindness in premature infants. In the 1940s, supplemental oxygen administration became a popular practice when doctors noticed that increasing oxygen levels converted the breathing pattern of premature infants to a "normal" rhythm. Unfortunately, there is a causal relationship between oxygen administration and retinopathy of prematurity (ROP), although this relationship was unknown at the time; thus, by 1953, ROP had blinded approximately 10,000 infants worldwide. Finally, in 1954, a randomized clinical trial identified supplemental oxygen as the factor causing blindness. Complicating the issue is the fact that too little oxygen results in a higher rate of brain damage and mortality in premature infants. Unfortunately, even today, the optimal amount of oxygenation necessary to treat premature infants while completely avoiding these complications is still not clear.

Conclusion

As these examples illustrate, there are many specific instances of environmental influences on gene expression. However, it is important to keep in mind that there is a very complex interaction between our genes and our environment that defines our phenotype and who we are.