Posts tagged: DNA

Are You Special?

Dr. Holzmacher's Business Logo for Orlandopsych.comAre you special?  Are you really unique, or a merely a unique assemblage of identical elements?  Identical twins are thought to be just that-identical.  Since they share the same DNA, there should be no physical or mental differences.  Strangely, this is not the case.  Identical twins do not have identical personality profiles.  Their physical resemblance is like a mirror when young, but subtle differences emerge with age.  Identical twins are not known to die on the same day, though born at the same time.  What could account for the increased differentiation over time?

At least one mechanism has been found to account for the observed disparity.  This biochemical mechanism may also explain wide physical and mental variations within any given family.  The initial groundbreaking work was performed by Dr. Barbara McClintock.  Even before the double helix model of DNA was discovered, Dr. McClintock revealed that regions of corn DNA could migrate to new areas of the DNA strand.  In effect, a unique corn genome was produced.  Identical strands of corn DNA produced seeds of different colors.  Her discovery added a page to the work of Gregor Mendel-the father of genetic inheritance.  Further discoveries reveal that this “jumping gene” mechanism is not unique to corn, or plants in general.  It occurs in many organisms-including humans.

The “jumping gene” mechanism in higher animals appears to differ from that of plants.  The plant DNA actually moves from one region of the genome to another; activating or suppressing protein transcription in that region.  The animal DNA appears to make a copy of the specific region, and reinserts itself in another area of the genome-just like plants.  The difference between plants and animals appears to be whether the region of DNA is removed or copied.

The “jumping gene” effect is most prevalent during the early development of the organism.  Cell division is occurring throughout the nascent brain, and the jumping effect cannot occur without cell division.  Within a few years of human maturation, cell proliferation only continues in a few areas of the brain; the hippocampus and the caudate nucleus.  Both areas are primarily devoted to the processing and storage of sensory memories.  Thousands of such “jumping gene” events have occurred over the course of a normal life.  This suggests that the human brain is genetically altered by new experiences, even in genetically identical twins.

The favorable aspect of “jumping genes” is its ability to assist the organism in adjusting to a changing environment.  The unfavorable aspect is that a new combination of DNA elements may be harmful to the organism.  An unusual number of these unique “jumping gene” sequences of DNA have been discovered in the frontal cortex of schizophrenics.  These unique sequences of DNA are also increased in autism and Rett’s syndrome-a severe neurodevelopmental disorder.

Even though the “jumping gene” mechanism may have accelerated human evolution, it may also engender a greater incidence of dysfunction and breakdown.  ”Jumping genes” may have allowed the human lamp to burn ever brighter, yet rendered the flame less than reliable.  So, every human is special-right down to their DNA.  The dilemma arises in regard to the functional outcome of the genetic alterations.  Does a unique trait increase adaptation to the environment, or render the organism less than functional?  It is good to be special, but perhaps it is not good to be too special.

Is it Nature or Nurture?

Dr. Holzmacher's Business Logo for online psychotherapyThis famous phrase is often repeated in the halls of academia.  It has become particularly important since the discovery of DNA; nature’s mechanism to pass on traits to the next generation.  The question really asks to what degree are the traits we observe a product of DNA versus the environment.  Much like the mind and body, it is a dichotomy formed from two inseparable concepts.

Increasingly modern genetics has demonstrated how DNA is influenced by the environment.  Identical twins share the identical strands of DNA, yet exhibit unique traits as they grow older.  Proteins manufactured by the DNA template may encode information and influence subsequent protein transcription in ways as yet unknown.  In the early days of genetics, much of the DNA code was labelled “junk,” but subsequent research increasingly proves otherwise.  Moreover, the longevity of each cell has been shown to be influenced by the environment.  Cell death had been assumed to be programmed from birth, but it is now known that diet and lifestyle influence the core program.

On the other hand, the opposing process can be observed in the average American family.  Even though family members share a nearly identical environment, each person is physically and mentally unique.  Among identical twins, the inheritance of schizophrenia is only around fifty percent.  If one identical twin develops schizophrenia, there is a fifty percent chance the other will fall ill as well.  All other mental impairments, assumed to be congenital (from birth), exhibit less gene penetration than schizophrenia.  The good news is that there is no congenital mental problem that affects over fifty percent of identical twins.  Among nonidentical siblings, the incidence is always less than twenty five percent, which is what would be expected if both parents carried a recessive gene for a mental illness.  If the child of suspected genetic carriers is reared in a different environment from the family (adoption), then the percentage typically falls below statistical significance.

Let us assume that schizophrenia is the one proven mental impairment that may be passed from parent to child.  Even when reared apart, identical twin children of schizophrenic parents still have a nearly fifty percent chance of developing schizophrenia.  Other psychological and neuropsychological impairments typically fade away when the identical twins are reared in different environments.  Nonspecific environmental influences have ruined many a doctoral thesis.  A genetic predisposition to develop a mental illness is just that; a slightly greater risk to develop a mental or cognitive impairment than the average person in the population.  Of equal or greater importance is the environment that surrounds and influences the genetic information.  A genetically schizophrenic person is less apt to express the maladaptive genes when reared in a supportive and minimally stressful environment.  Conversely, when a strong a man as Admiral Bird was isolated at the South Pole, he began to hear voices and see images that were nonexistent.

There is no material that is impervious to the environment, and our genes are no exception.  The direction of current research has amplified the extent to which nature and nurture are reciprocal influences, down to the molecular level.  The genetic potential of the human brain has allowed us to shape and control the environment; more than any other creature known to this planet.  The future of biochemical research will allow us to increasingly alter our own genetic programming.  At this juncture, the nurturing human environment is directly influencing nature. Perhaps it is not wise to mess with mother nature, as the old saying goes.  Messing with mother nature has, it must be admitted, put humans at the top of the food chain.  We humans will “mess” with anything we can get our hands on, and nature is certainly close at hand.  Let us hope that she declines to “mess” with us.

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