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The Overpowering Influence of the Environment to
Gene Expression
By: Prof. Isidro T. Savillo
Savillo, I. 2002. The Overpowering Influence of the Environment to Gene Expression, http://www.oocities.org/gene_environment/index.htm
or at BIOLOGY BROWSER: Subject:Genetics
Introduction
The earth is similar to a universal biological incubator where all present day organisms are capable of living and reproducing. It is clear that our bodies… and for a meaningful rationale, our cells are subjected to various degrees, though each individual factor may differ from each other but not too far apart, of temperature, pressure, radiation, the stretches of days and nights, and other physical phenomena (e.g. the tilting posture particular to the revolution of the earth and works of the gravitational forces, the sounds of the passing
train, the visual perception of blinking lights, etc.) in a daily basis.
Much more, other factors, like pollution, diseases, food, traditional
components that have been gripped by so many, newly shaped cultures
as a result of newer trends in fashion, religion, government,
commerce, education or just any belief or talent which has sprouted
also nudge our cells. These factors, we see and feel around us. Its
integration to our bodies via our senses or through the alimentary
canal or other openings in our bodies like skin pores, etc. has brought
direct or indirect contact to our most precious property inside our
cells , Our Genes.
Our genes are nothing more than the DNA and RNA of the viruses.
They could be separated as non- living entities in a laboratory bench.
They need various factors around them so as to attune themselves for
expression. These factors, biological and physical , complete or
deficient, having broad or narrow ranges, mixed in various
proportions, in a particular time frame or cycle, would bring
characteristic results of expression, as we basically know, could be a
phenotype for structure, function or behavior. In this paper various
theories which are supportive and deductive to the given statement on:
the overpowering influence of the environment to gene
expression will be discussed.
The Cell and the Molecular Biology of Natural Selection
The didactics on natural selection of various species of organisms
are mostly organismic. There was not much discussion on the cellular
and molecular aspects because its effect or the “incubation period” of
a phenotype change can take place for centuries. These are passed
from one generation to the other until there will be a favorable
synchrony between the physical and the biological elements for the
final type of progeny to significantly survive. To a greater perspective,
it is the physical which controls the changes in the biological organism.
As we all know, in three methods of speciation: parapatric, sympatric
and allopatric, the external factors maneuver the changes.
The Definition of Environment
There are two types of environment. The first is the Exogenous
Environment and the second is the Endogenous Environment. The
Exogenous Environment is the external environment. This consists of
the various physical and chemical factors (abiotic sources) that we
“sense” with our senses and the biological elements which are not part
of our own genes. They could be the genes or products (philosophies,
food, etc.) of genes of other organisms which surround us. On the
other hand, the Endogenous Environment comprise the genes or the
product of our own genes and the physical factors which resulted
from our own cellular metabolism.
Endogenous and Exogenous: Which of the two is superior?
These two factors are inseparable toward their roles in the
expression of the genes. As we all know in biological laboratories,
cells or organisms or even in cloning, we need to subject the biological
materials in ambient conditions so we can expect a fruition of our
work. The ambient condition is represented by the exogenous
environmental factors and subsequently, the latter, in living organisms,
influence the endogenous factors to operate favorably so as to attain
fruition. This could not eventually be felt because the exogenous
factors have wide ranges of tolerance by the cells that’s why the
mechanisms could just automatically work. In this sense, the
exogenous factors are superior over the endogenous factors as to
their roles in gene expression. Any gene expression is influenced by
these two environmental factors.
Overview of Gene Expression
Anything which represent the phenotypes (e.g. any feature or action
perceived in an individual) of the organism is a product of gene
expression. Even phenotypes that are ephemeral and speedy and are
considered “neural” in nature. For the latter, the mRNA for the basic
needs are produced in advance to warrant urgent biological
responses.
The Environment and Its Effect to Human Behavior
Behavior is a product of learning that has been repeatedly
patterned in the brain. To learn is to expose our senses to exogenous
factors that we can sense per se. These are then subsequently
processed by the endogenous factors prior to their functions of
putting up a phenotype for behavior. Moreover, Behavior can be
regulated or developed by thinking. Changing is impossible for a
behavioral phenotype that has been previously experienced.There
are tendencies to reclaim those past behavior once conditions
become favorable.
A) Thinking as an Environmentally Induced Phenomenon
Thinking is a tool needed by higher organisms so as to gain
“satisfaction” during the course of their existence. Through thinking
one could find answers to questions bisecting him in the society or
community. It is through thinking that one can regulate, or develop a
new behavioral phenotype to whatever suit him. Thinking could only
be -constructed through the learning experience of the past. The
images and ideas were part of the environment and these were
molded to create a thought normally or abnormally. Thinking is
regulated by a complex of genes. When an individual , e.g higher
forms of animals, thinks, it is always for his own advantage whether
the resulting action or expression is favorable or not to the onlookers
or observers.
B) Defective Genes
There are two phenotypes for defective genes. The gene is present
and causes a defect and the gene is absent, and causes a defect. For
the former, the presence of a defective gene could be regulated by the
environment for better or for worse. If the gene is present in the
individual but this is not expressed, then the gene is still in the
regulated status. The introduction of exogenous factors and
subsequently, endogenous , may trigger its expression. If the gene is
absent, the accumulation of products of other genes in the metabolic
pathway causes the defect. The exogenous (e.g. environmental)
factors (e.g. adding the missing protein, cloning the missing gene,
proper rehabilitation of the patient, etc.) could lessen , cover-up or
efface the effect of the defective phenotype depending on the degree
of suitable application in a favorable setting with the endogenous
factors. Environmental factors (e.g. taking more lactose for a lactase
deficient person) could also amplify the defect.
The Environment and Its Effect to the Physiology of Cells
As previously mentioned, genes are influenced by the exogenous
and, subsequently endogenous factors for all. In molecular biology ,
there are two types of genes in accordance to gene expression. There
are genes which need to be induced and those genes which do not
need an inducer, therefore calling the latter as constitutive genes.
(Alberts et al, 2000). Nevertheless, whether the genes need an inducer or
not, they are still affected by both the exogenous and endogenous
factors for their expression.
A. Gene Expression
1) Clones and Monozygotic Twins – Though these
examples of individuals are believed to share more or less
similar genotypes, the environment still would influenced them
to exhibit different sets of phenotypes. No two individuals are
alike phenotypically, taking all things for granted. 2) Distinct
Individuals- A distinct individual has its own set of
phenotypes because of his own characteristic genotype.
Moreover, the bombardment of environmental influences will
transform him to what really is “he” in this world. 3)
Defective Genes- Please refer to the former section.
The Environment and Its Effect to Our Structural Framework
This is a very common observation and in fact one that supports the
theory of natural selection. For instance, the Native Indians of the
Americas were once miners as their occupation for long. As times go by, there were genotypes formed as a result of extensive
underground exposure and these were passed on to their progenies.
These phenotypes include short stature and expanded chests (Gould and Keaton, 1996).
Conclusion
The environment has a greater role in establishing a precise
phenotype for a certain organism. The environmental factors,
exogenous and endogenous , follow a cascade mechanism affecting all
active genotypes resulting to a complex phenotypic characterization of
the individual. Though this paper could not cover all examples in the
three categories mentioned ( human behavior, physiology of cells and
structural framework ) , it has given an insight on the power of the
environment for a tight grip on the three phenotypic expressions.
Recommendations
There must be a universal application of environmental genetics to
all organisms. After thorough DNA sequencing and mapping of the
chromosomes of the various organisms including humans, I would
suggest molecular, cellular, chromosomal, genetic, organismic and
environmental ( bio-chemical, physical, philosophical, etc.) analyses in
an interdependent fashion so as to be able to know the actual processes
involved in the making of the final phenotype of an individual.
I also would recommend reading the article by Kenneth Schaffner
entitled “Can There Be Purely Genetic Explanations?” in a book
entitled “Behavioral Genetics” (Carson and Rothstein, 1999).
References
Alberts, B., D. Bray, J. Lewis, M. Raff, K. Roberts and J. Watson
2000. The Molecular Biology of the Cell, Garland Publishing,
Inc.
Carson, R.. and M. A. Rothstein. 1999. Behavioral Genetics. The
Johns Hopkins University Press.
Gould, J.L. and W. T. Keaton. 1996. Biological Science.W.W. Norton and Company, Inc.
A New (2003) Article!!!
The Role of the Environment: A Twist in Genetic Expression by Isidro Savillo
Please Note: Any Idea Taken from this Paper, "The Overpowering Influence of the Environment to Gene Expression" Without Citing the Author and the Source where It was Taken , is Strictly Prohibited.