Dark Side: Gene Behavior

 

How do genes affect behavior? To begin to answer this question, it’s important

to understand some basics about genetics.

 

There are approximately twenty thousand genes in the human genome. The genes are located in forty-six chromosomes (twenty-three pairs), one set in the pairs derived from the mother, one set from the father, in the nucleus of most cells of the body. The only cells that don’t contain all forty-six chromosomes are the germ cells in the testes or ovaries, each of which has twenty-three chromosomes, or half the number in the somatic cells. Cells that contain all forty-six chromosomes are called diploid cells since they contain both pairs, while germ cells are called haploid.

Chromosomes are composed of DNA, the master blueprint of a cell. DNA is coded on the sequence of four different chemicals called bases. The bases sit in pairs with T (thymine) coupled with A (adenine) and G (guanine) coupled with C (cytosine). The forty-six-chromosome (diploid) genome contains over six billion base pairs. Sequences of base pairs, called genes, code for and produce gene products such as proteins. If just one of the base pairs is altered by mutation, say from ultraviolet damage, a virus, or cigarette smoke, the resulting protein will be aberrant, and usually faulty. Some of these mutations are not fatal and are actually kept by the cells and the population. These are called single nucleotide polymorphisms, or SNPs.

There are about twenty million SNPs found in humans, and they account for many differences in the appearance and behavior of people, from curly hair of traits and diseases has focused since the 1990s. Other important alterations to the genetic code involve so-called promoters and inhibitors, pieces of genes that regulate the gene’s ability to make products. Some of these products regulate the behavior of neurotransmitters. So promoters inhibitors are like the gas and brake pedals of a gene as they control the delivery of neurotransmitters like serotonin and dopamine in the brain.

For serotonin, implicated in depression, bipolar disorder, sleep and eating disorders, schizophrenia, hallucinations and panic attacks, as well as psychopathy, the breakdown enzyme is MAO-A. MAOA, the gene that produces this enzyme (and lacks its hyphen), has a promoter that comes in either a short form or a long form. The version of the MAOA gene with the short promoter has been associated with aggressive behavior and is called the “warrior gene.” There are probably twenty to fifty or more SNPs involved in causing most diseases. Therefore, statements that the warrior gene “causes” aggression, violence, and retaliation raises the hackles of geneticists, since there are probably dozens or more “warrior genes” in people who are particularly violent. But even the simple diseases (called Mendelian diseases, after the godfather of genetics, Gregor Mendel)—like cystic fibrosis, which is caused by a single mutation in the gene that codes for the chloride channel in cell membranes regulating water balance in the lungs and gut and glands—can appear as fifty different disorders in fifty different individuals with the disease. In the case of cystic fibrosis, that single chloride channel mutation affects other cellular and organ components. The gene-gene interaction, or more correctly gene product– gene product interaction, is called epistasis, and this effect must also be considered when determining the causes, symptoms, and cures for diseases of all kinds, even psychiatric disorders.

The neurotransmitter dopamine is implicated in several psychiatric disorders. Drugs that increase dopamine transmission can alleviate symptoms of depression, and drugs that reduce it can alleviate schizophrenia. The impetus to initiate a behavior “considered” by the prefrontal cortex is largely under the energetic control of dopamine, which is mostly produced in the midbrain. When dopamine is released, things happen. Dopamine doesn’t decide exactly what will happen, but how quickly and strongly something happens, and for how long,  much like an accelerator pedal on a car.

How much the monoamines such as serotonin and dopamine affect each person depends on the person’s genetic makeup and the maturity of the underlying circuitry—especially for the genes that control the synthesis of these neurotransmitters—but much more importantly on the enzymes, such as MAOA, that break them down and terminate their synaptic action.

Thousands of types of prefrontal cortices can possess different amounts of highly variable traits such as memory, emotionality, aggressiveness, and sexuality. Likewise, because of all the genetic variables, there are really a limitless number of ways to be schizophrenic or depressed. Some prefrontal disorders are more complex than others, and certainly schizophrenia is one of the most complex. But there are also probably many ways to be a psychopath, too, considering all of the combined neural systems and genetic factors involved. Unfortunately, very little is known of the biological basis, especially genetics, of the brains of psychopaths.

Despite the impressive numbers associated with the human genome, the information carried on those twenty thousand genes, forty-six chromosomes, and six billion base pairs tells only 5 percent of the story. The remaining 95 percent resides in a still-mysterious garnish of noncoding nucleic acids, bits of DNA and RNA that are now believed to profoundly affect what ultimately is produced by the genetic code in the nucleus. They help direct the functions of the cell, the social interactions between cells in tissues and organs, interactions between organ systems—and what a psychopath dreams and schemes and does to others in his everyday predatory wanderings. One way to look at the way the genetic information is actually laid out in the nucleus of cells is quite different from how we all learned it, with all the forty-six chromosomes tightly coiled into their classic X shapes during a brief phase of cell division.

These nongene structures are now thought to be at the causal root of some disorders, including schizophrenia, depression, and addiction, as well as many forms of cancer and immune disorders. These elements appear to have been taken up from other organisms such as viruses and bacteria during our evolution, but also from the foods we eat.

One implication of the existence of these noncoding genetic regulators is that even if we do determine the coding gene combinations that underlie psychopathy, there will still be a million or more combinations of these with the noncoding nuclear elements that we will then need to consider in order to understand the real genetic basis of psychopathy. But we do know some things.

Acknowledgements:

www.politie.nl  and a Chief Inspector – Mr. Henk van Essen© from 1th of March 2024 new Politiekorpschef  Janny Knol

www.aived.nl    AIVD – Mr. Erik Akerboom ©

 

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