Inheritance | Sharon Moalem


Book published: 2014

Goodreads Bookdepository

In 1975, Arthur Riggs and Robin Holliday came almost simultaneously, but individually, to the conclusion that even if genes were fixed, they could give different expressions in response to stimuli. It took another 25 years before these ideas gained wider acceptance. Researchers are now beginning to understand what our genes do to us and what we do to our genes.

FLEXIBLE INHERITANCE. Conditions can be hidden and identical genes in different people do not always behave in an identical way despite the exact same set of DNA. The idea of flexible inheritance teaches us that it is possible to accept and reject our heritage. The concept of variable genetic expressivity is about how someone is affected by a genetic mutation or condition.

“While it may not always be possible to break completely free from your genetic inheritance, the more you learn, the more you will come to understand that the choices you make can result in a big difference in this generation”

DNA IS CONSTANTLY CHANGING. Just like a company with “just-in-time” delivery, people avoid unnecessarily stockpiling. For example, enzymes are biologically expensive to produce. Just because you have inherited the genes for an enzyme does not guarantee that your body will use it. Like thousands of small light switches, some are on while others are off. All in response to what you do, what you see and what you feel. The body is in a constant state of transformation and renewal where experiences leave a mark in your genome. Memories, feelings and expectations are coded, like a comment in the margin of an old book, in all cells.

 “Exposure to raditation during routine air travel, ultraviolet radiation while working on your tan, ethanol in your cocktail, chemical residues in tobacco smoke, insecticides, and chemicals in your personal care products, are all examples of general factors that can damage your DNA. How you choose to live will determine how well you treat your genome”

EPIGENETICS. Everything from mutations to small epigenetic modifications can alter the expression of your genes. Geneticists have developed a number of ways to study and reprogram methylated genes – to turn them on and off or to turn the volume up or down. The hundreds of trillions of synapses in your brain that cause this to happen are transitions between nerve cells and cells. The signals used to communicate must be replaced over time and fed with small doses of chemicals created by your body. Many neurons are looking for new connections as well as maintaining decades old connections. 

BULLYING LEAVES TRACES. Twin-studies have shown that if one has been bullied in adolescence, a gene called SER is affected (lowers the amount of protein produced). These epigenetic changes are believed to be able to continue for life. Cortisol is known as the stress hormone and is normally elevated in people under stress (a peak of cortisol can help us through a critical situation). But having too much cortisol for too long can short-circuit our physiology. The epigenome was altered in response to protect them from too much prolonged cortisol. The bullying reduced cortisol levels when the child was stressed.

TRAUMA CAN CHANGE GENES. To see how childhood trauma can affect gene expression, researchers in Zurich separated young mice from their mothers for three hours every day for two weeks. Once adults, these mice had difficulty evaluating potentially hazardous sites. And when they were placed in unfavorable situations, they gave up instead of fighting. Most notably, they transmitted these behaviors to their children. A trauma in one generation was genetically present two generations later. A mouse’s genetic predisposition is 99% similar to that of humans.

QUEEN BEE NOT GENETICALLY SPECIAL. A queen bee and her workers can come from the same parents and they can have completely identical DNA. Nevertheless, their behavioral, physiological and anatomical differences are large. This is because the caterpillar queen eats better.

FOOD AND DIETS. Every year, tens of millions of Americans try to change their diet. Often without a thought of finding out which diet is genetically correct for them. Even two persons of the same sex, age, ethnicity, height, weight and general health probably have very different needs when it comes to calcium, iron, folate and a variety of other nutrients. Our genetic heritage affects our dietary needs – called nutrigenomics.

NOBODY IS AVERAGE. A letter change in a series of billions of letters, and you have legs that break with the slightest pressure. A small shift in one of our genes can completely change our lives. There are those who are hereditarily fructose intolerant. Supplementation with fish oil can be good for some and very bad for others. What is good medicine for one person may be bad for another.

“The answer is that were all individuals when it comes to our genomes, and completely unique when it comes to our epigenomes and even our microbiomes. We can and should investigate our genes, and metabolism, for clues about what would suit us best”

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