The topic of epigenetics has been floating around in scientific circles for years now. After renewed interest at the turn of the 21st century, research into the field has become much more common. However, epigenetic research has been around much longer than many suspect, and the controversy dates back almost as far. Between cancer diagnoses and the possibility of inheriting your ancestor's acquired traits, a lot is going on in this field.
Epigenetics is the process cells use to express a gene. It tells the cells which gene to turn “on” and when. Epigenetics also tells the cells which genes to shut off. An epigenetic change is a change that overrides the DNA. In Latin, the prefix “epi” means “upon” or “over.” Instead of changing the DNA itself, it changes the way the cells read the DNA. Essentially, epigenetics change the instruction manual — the DNA — to change the directions cells receive. These changes can be positive or negative, caused by environmental or internal factors.
The term “epigenetics” was coined in 1942 by the embryologist C.H. Waddington. The meaning wasn't exactly the same as today but was still centered around biological development and how genetics manifest traits. Some modern scientists believe epigenetic changes can affect not only the person in whom the change occurs but their offspring as well. This references 19th-century biologist Jean Baptiste Lamarck's disproved theory that traits acquired throughout a lifetime can be passed down to an organism’s offspring.
Transgenerational epigenetic inheritance refers to the possibility that genetic changes — not changes to the DNA but changes to how it is expressed — can be passed down from parents to offspring, and maybe even further. This theory suggests factors that influence an individual’s health during their life could have implications for generations.
A study by postdoc student Brian Dias exposed mice to a chemical with a sweet smell and then gave them a mild shock. The mice became fearful of the smell, and their offspring appeared to show a sensitivity to it as well. The grandchildren of the original mice also showed a physical reaction when they were around the smell. Dias also observed a physical change in a certain part of the kidneys in all three generations of mice. He believes this could be an instance of transgenerational epigenetic inheritance.
Plants such as tomatoes and maize have edits in their genes that are not a part of the DNA but instead affect how it is translated. For example, maize is susceptible to a mutation that makes its leaves pale instead of green. However, epigenetic changes turn this mutation off, so that’s it’s not expressed. Similarly, some tomato plants express a gene in a certain way to affect ripening times.
There are few epigenetic studies in humans, both because of ethical dilemmas and the difficulty they would present. In women, scientists would have to study at least four generations to determine whether an acquired characteristic or epigenetic change during the lifetime of the first generation would affect subsequent generations. In men, because sperm is continuously regenerated throughout their lifetime, researches would have to study three generations. Such studies would be a huge time and financial undertaking with countless potential factors for which to account.
Some studies appear to support the idea that epigenetic traits are passed down throughout generations, and some don’t. For instance, a study of Swedish historical records seems to indicate that men who experienced famine as children had children who were less likely to have heart disease or diabetes. However, it is hard to determine the epigenetic correlation behind these changes, if there is one at all.
Epigenetics pertains to how a cell reads a gene. Some epigenetic abnormalities, along with genetic alterations, can lead to cancer cell formation. A disruption in the expression of a gene, or a disruption in the epigenetic process, can also lead to cancer. However, since epigenetic changes can sometimes be reversed, scientists are hopeful that epigenetic therapy can help treat cancer.
Since the theory of inherited epigenetics is based on the idea that acquired traits can be passed down through generations, many scientists object to the dubious and preliminary findings. They point to the fact that Lamarck’s theory has long presumed false, and that there is insufficient evidence to back up the idea that epigenetic traits can survive the explosive growth a fertilized egg undergoes. However, few scientists deny that epigenetic changes during a person’s lifetime influence that person’s health and genetic manifestations.
Scientists continue to look for ways that epigenetics influences health, lifestyle, and genetic code. It is possible that these studies will lead to great leaps in disease research. As for the present, scientists are looking into the ways epigenetics affect individuals, and how it can affect their offspring.
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