Weird Science: Epigenetics

by Sue Lange
I was inspired a while back by the challenge in sfsignal.com to science fiction writers to work with current science. Even though Anthena Andreadis was talking about science fiction, it gave me an idea for this non-fiction-about-science series of blog posts. I picked one of the topics she mentioned: epigenetics. It’s weird and appropriate.

In a nutshell epigenetic traits are changes in gene expression (what something looks like for instance) that have not occurred through changes in the DNA. It’s easy to see how environment affects our bodies after we’re born. We break legs, contract diseases. These things change the way our bodies look and function. What’s weird is that sometimes these changes due to environment can be passed on to offspring. Doesn’t that just fly in the face of everything you learned in Genetics 101?

As self-respecting denizens of the 21st Century, we pooh-pooh Lamarck. The Lamarckian model of evolution has the giraffe coming into being after generations of horses slowly stretched their necks through lifetimes of eating leaves higher and higher on the trees. One individual’s neck grew slightly longer in its lifetime and that slightly longer neck was passed on to the offspring whose neck also elongated slightly in their lifetime. After several lifetimes of slight neck stretches, voila! we have a long-necked horse.

How silly. Us self-respectors subscribe to Darwin and Mendel nowadays. Inherited change occurs in the genes rather than in the bodies of the gene expressors: the people. Or the animals.

But hold that thought. There is evidence afoot that we CAN inherit changes that come about due to environment acting on the phenotype rather than mutation in the DNA acting on the germ cells. We call that process Epigenetic Inheritance, and to this biology-major, college-graduate, that’s just weird.

Here’s a quick rundown of the classic example for epigenetic inheritance posted by the Institute of Science in Society:

“In the nest, the mother rat licks and grooms her pups, and while nursing, arches her back to groom and lick her pups. Some mothers (high performers) tend to do these more frequently than others (low performers). As adults, the offspring of high performers are less fearful and show more modest responses to stress in the hypothalamus-pituitary-adrenal (HPA) neuro-endocrine pathway.

Cross-fostering studies showed that the biological offspring of low-performers reared by high-performers, resemble the offspring of high performers, and vice versa. …

Amazingly, the pups of both high and low-performing mothers start out life genetically the same.”

There are other examples out and about. Children of holocaust survivors develop diseases they would not have developed had their parents not been malnourished during part of their lives. Fruit flies exposed to harsh chemicals grow bristly eyelashes (obviously these scientists are working with bodacious microscopes to be able see that) and then their younguns grow bristly eyelashes too.

When details of the methods for inheritance are explained, often I have a hard time deciding if this is something different than regular inheritance via genes. It seems to involve the DNA somehow. The difference between the two mechanisms is too subtle for me to happily accept a Lamarckian model. It begs further investigation.

Regardless, whatever is going on is certainly weird and proves once again that the more we discover, the less we know. It’s sort of a built-in feature of science that keeps us coming back for more.

Science Daily nicely illustrates this weirdness that is scientific study generally and epigenetics specifically in the title of their 2009 article, “100 Reasons to Change the Way We Think About Genetics.”

Sue Lange
Sue Lange’s latest ebook, Tritcheon Hash, is full of lapses of logic and weird science. Sample the book right here at BVC.

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Weird Science: Epigenetics — 6 Comments

  1. I can just wrap my head around this if I think certain conditions will affect genes in a way that changes how they are passed on to offspring.

    The rat study seems to me to be a little different. It sounds to me like a biological argument for nurture: that is, certain kinds of nurture have a biological effect, not just an emotional one. Or maybe emotional effects are biological.

    Anyway, you’re making my mind reel early in the morning, which is probably the point of these posts!

  2. And it becomes even grayer, if you start thinking about people. Human behavior is partly cultural — but what part? Consider, oh I dunno, Mitt Romney. He is descended from generations of prominent Mormons. Is it a surprise that all his sons are Mormons? Was it nature, or was it nurture? Why did it make no difference that Mrs. Romney was not born a Mormon but converted upon marriage?

  3. The way I had this explained to me in a Interpersonal Neurobiology science class is that it’s not really Lamarckian. It ties into what’s been called “junk DNA.” Which ends up not really being “junk.” The genetic tendency exists and the environmental conditions modify the DNA.

    Essentially, epigenetics makes a case that emotional environmental effects affect the genetic expression, just like other circumstances we know about. When you think about the biochemistry of emotional stressors within the body, it makes sense that either soothing or stress could modify the genetic expression of a trait. Lamarck wasn’t talking about emotions, IIRC. Most of the stuff I’m hearing about epigenetics (granted, this comes from an IPNB perspective) focuses on emotions affecting genetic expression.

  4. My doctor explained it as also the expression of recessive genes that an individual is carrying when previously dominant genes have been in control.

    I started researching this because in the course of dealing with a catastrophic illness, my body made an epigenetic shift and became severely gluten intolerant. The doc said that when this happens. not only does the individual stay that way the rest of her/his life — any offspring will also express the recessive genes.

    I’m going to use it in a fantasy novel I’m researching!

  5. The wiki article on epigenetics is very good:

    http://en.wikipedia.org/wiki/Epigenetics

    To quote it: “[epigenetics] refers to functionally relevant modifications to the genome that do not involve a change in the nucleotide sequence.”

    What’s relevant here is that the genome sequencing is not changed but its expression is.

    We tend to think of the DNA packaged in sperm and eggs as inert. Instead, it is primed and ready for a specific set of division. The egg is even more primed than the sperm. Consequently, one of the areas where epigenetics shows up most obviously is the embryology of the developing animal.

    That said, I strongly suggest a very critical perspective on something as emergent as the effects of emotions on epigenetics. Emotions reside primarily in the brain and affect the body largely indirectly. There’s not a lot of difference in the physiological response to adrenaline from fear or anger though we may experience them very differently.

    Stress does appear to have an epigenetic effect though it’s not all clear how that effect is expressed. The malnutrition studies, and the holocaust victims, were extreme examples of stress.

    The epigenetic mechanism I understand the best is DNA methylation– the adding of a methyl group (-CH3) on the side of a section of DNA. This can affect the expression of a gene. “Expression” can mean on, off or on/off under specific circumstances. The sequence of the DNA is unchanged so if the methylation is reversed, the expression of that gene is affected but the production of that gene, when expressed, is unchanged.

    If, for example, methylation occurs in the DNA that produces the packaging proteins in either sperm or egg production we can get effects that are quite different from what we might expect. To make an analogy, we can affect the shape of the head light. Or, we can affect the robots that make the car itself.