The Processes by Which Genes and Environment Interact to Influence Development

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‘Genes’ refers to units of heredity information that consist of DNA
and are located on chromosomes and can exist in alternative forms
called alleles (
‘Environment’ according to The American Heritage Dictionary of the
English Language, Fourth Edition states: “[Environment is] The
totality of circumstances surrounding an organism or group of
organisms, especially: the complex of social and cultural conditions
affecting the nature of an individual or community.” A child grows to
possess a detailed nature which obtains that particular form due to
the effects of two major contributing factors. The first influence
comes from the genetic structure which he inherits from his parents
and the second looms from the collective experiences he has from his
daily social interaction with his surrounding environment. The first
section of the essay will present an insight on the influences of
genetic as well as environmental factors on child development. This
section will illustrate the different aspects of child development
that are best understood within an epigenetic framework and how
theories of child development ‘escape’ without considering gene
environment interactions. The second section will discuss the
interplay between genes and environment and their significant
contributions in a child’s development such as intelligence and
acquisition of ‘cultural tools’. In this section, we will look at the
concept of individual differences, the importance of learning their
existence and how biological processes affect individuality through
the study of the transactional model.

The theory of evolution is a useful approach to understand what
aspects of a child develop during his lifespan and how they occur.
Evolutionary theorists believed that development simply reproduces
what was present in the previous generation and will be unchanged in
perpetuity. Humans, however, change in many ways. They develop
physical and psychological characteristics, each having its own set of
causes and development.

Our physical appearances and gender are a result of genetic influence.
Females have two ‘X’ chromosomes while males have one ‘Y’ and one ‘X’
chromosome. Differences in physical development due to chromosome

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"The Processes by Which Genes and Environment Interact to Influence Development." 28 Mar 2017

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differences are used to distinguish the sexes. The child’s physical
characteristics are alike to his parents in all essential structures
like the heart and functions like the circulation. Genes are
transmitted from the parents to the child. They are complex chemical
structures known as DNA and are located in the nucleus cell where they
formed long strings known as chromosomes. The role of genes acts as a
template against which enzymes can be constructed. These enzymes then
act as the ‘worker’ molecules of the cell to bring about chemical
reactions to make new cell parts. There is direct correlation between
the structure of genes and enzymes and this structural encoding is the
important ‘information’ carried by the genes. Different cell parts
serving different functions communicate with each other, became
reflected in the nerve tissues, functions and in the characteristics
we can observe, thus, development of most characteristics is
influenced by the information in large numbers of genes. Different
genes are transferred from each child of the same set of parents. For
this reason each child bears more similarity to his on her blood
relatives than to anyone else. At the same time there are also many
differences amongst blood relatives. Only identical twins
(monozygotic) have identical chromosomes and genes as they are formed
by duplication of a single zygote. Twins who are not similar to one
another (fraternal twins), develop from two separate zygotes
(dizygotic). These fraternal twins may resemble each other, like any
brother and sister, but they will also be different from one another
in many ways. The reasons for our genetic variations in physical
characteristics are due to natural selection and adaptation. The
former suggests that random genetic variations are produced and passed
to the next generation and produce corresponding variations in each
developing characteristic called phenotypes. For instance, child
receiving strong manual dexterity genes grow up to be good tool-makers
and these set of genes will be passed on to the successive generations
(Richardson, K., 2004). Natural selection tends to purge genes
unfavourable to survival and genetic variations lessen. However, it
allows variation in characteristics less crucial to survival to
accumulate. That is why the son may have his mother’s cat-like eyes
and the sister, the father’s onion nose implying genetic physical
variations between their mother and father yet share among themselves
and their parents many common characteristics. Adaptation implies that
some phenotypes are selected to adapt to particular environment. In
the theory of attachment, the child is believed to have a
genetically-determined psychological characteristic that predisposes
him to be attached to his caregiver (Richardson, K., 2004). Physical
characteristics appear to be specialized adaptations for instance, the
ears are for hearing, while psychological characteristics are more
generalized such as language used for communication, transactions and
public interactions.

The evolutionary and genetic concepts suggest that development is
biologically predetermined from the starting process to the endpoint
and there is nothing much we can do to change them. This development
implies a fix potential to every characteristic development. This
view became known as genetic determination whereby information carried
by genes determines every level of development from the tissues,
nerves, organs up to psychological characteristics. However, many
psychological characteristics such as temperament, intelligence and
language acquisition do not follow this development track as their
course of development are unpredictable and keep on changing
throughout life itself due to environmental changes and experiences
from socialization with others. The behaviours of organisms
continually changing their environment and humans adapt the
environment to themselves. Genetic determination theory could not
ensure adaptation in highly changeable environments thus; more
adaptable systems are needed to describe such adaptability.

Systems such as the epigenetic development allow children to take a
more adaptable developmental pathway. Psychological development is
best understood within this epigenetic framework. In this model, genes
‘switch each other on or off’ according to feedback from the internal
cell of characteristics and the external physical world, the
surrounding environment. An example of such life-long developmental
plasticity is the learning process of a child such as language
acquisition, games and practical skills have this adaptability
structure. Very young children are able to acquire and use such skills
in their social-emotional regulations and reasoning. These
psychological characteristics are not fixated and continued to change
throughout lifespan thus, their progress are better understood within
an epigenetic frame than genetic determination theory whereby the
behavioral characteristics are determined and thus, difficult to
adjust to changing environment.

In Gesell’s Principles of Development (Cain et. al, 1992), he believes
that a child’s development is determined by the action of the genes
through a process of maturation and environmental factors play no
direct role in the chronological unfolding of structures and action
patterns called genetic programs. In this theory, environmental inputs
have insignificant influence on the course and endpoint of
development. The reason for such inclination towards genetic
programming is that evidence for its existence in physical structures
and behavioral characteristics in non-human animals is very strong.
The human primary and secondary sexual characteristics seems to abide
to the sequence of the genetic clock. Some behaviours which occur in
the human infant are not caused by external stimulation. The
internally caused actions are crying, stretching, sneezing, chewing,
and smiling. At the time of birth, certain specific responses to
external stimulation can occur. These are called reflexes. When the
bottom of the baby’s foot is scratched by the fingers, the toes of the
baby are extended. This is called the Babinski reflex. Thus, the
theory of genetic programming ‘escape’ without considering gene
environment interactions as to the proponents, the role of environment
in physical development of an infant is of insignificant value.

Though there is little evidence for genetic programs to exist in the
sphere of psychological development, the theory of Nativism by Chomsky
argued that for the correlation between physical and mental growth of
an infant is of a close one. His argument was that the experiences an
infant has from his external surrounding (physical environment) is too
bland to elucidate the very complexity of human mental psychological
characteristics. Gardner’s Multiple Intelligences’ theory (1983, cited
by Richardson, 2004) suggested that the development of intelligence
involves the developmental growth of innate ‘computational systems’ in
the brain which progress according to biological timetable.

In the reading extract of “The efflorescence of adaptation” by Alan
Newell (cited in Richardson, 2004), he argued that humans invent new
response functions creating an efflorescence of adaptation. We create
new job scopes, sports and recipes and these are further develop to
attain newer function response for instance, the creation of recipes
and from these recipes, came the inspiration to write on different
ways to prepare each recipe. Genetic programs fail to account for
these adaptable encounters as behaviours in the former is seen to be
fix and predictable. The weak empirical evidence (mainly from
observations and not controlled experiments) for genetic programs for
psychological characteristics made it possible for alternative
explanations to be accepted.

The environment influences physical development such as factor of
nutrition is essential for the physical growth of an infant.
Inadequate diet and nutritional deficiency of the mother increases the
risk of congenital defects, still birth and infant mortality during
the first year. Prolonged and severe emotional stress of the pregnant
mothers increases the chances of miscarriage, premature delivery and
temperamental state of the babies. Besides the maternal
characteristics, a number of environmental agents such as diseases,
viruses, drugs, chemicals and radiation can adversely affect the
prenatal development and produce birth defects.

The influence of environment on the development of the child for
example, the love for music, is referred to as nurture. A child learns
to do things for which he gets praises and does not do things for
which he is punished. Both views contained some truth but neither is
complete. To understand the development of a child, we have to study
the complex interaction between heredity and environment. For example,
a child is born with a talent for music. In the child’s family, this
talent for music is expressed by the child at an early age, through
his activities of listening to music. The parents notice the child’s
interest in music and expose the child to more music by giving him a
toy musical instrument say, the violin. The child’s interest in music
grows further and his talent develops and the parents offer even more
musical experiences such as having home violin lessons. This has a
further positive effect on the child’s talent and his desire to play
music. It is thus clear that both the child’s inherited talent and
environment shaped his development. The child had the talent for
music, but this led to a change in the environment by making his
parents provide more musical experiences at home. Now these
experiences in the environment further developed the child’s talent
and motivation and made the parents introduce more musical experiences
to the child. The process goes on in a form of transaction. This
approach to understanding development is called a transactional model
of development. The model is able to explain why siblings, though
physically in the same environment, always grow up in different ways.
This simply means that the environment of family life is always
changing in the process of adjusting to the personalities of its
members. A child who displays temper tantrums has a very different
experience with his parents as compared to his easy going sister.
Based on the transactional model of development, the child changes the
environment which in turn changes the child. The child’s development
is like a complex dance in which nature and nurture both lead, and are

Such interactions are important in psychological development however,
they also make ‘causes’ of development and interventions far more
difficult to identify. Development psychologists cannot reduce all
characteristics to a model of gene-environment basis as this is only
appropriate for simple physical characteristics. The acquisition of
‘cultural tools’ and psychological characteristics such as
intelligence cannot be explained by genetic determination and need
more complex epigenetic models.

What the child acquires from ‘cultural tools’ are models of social
interaction and this can come from the practice of tangible
instruments such as a spoon. At first, the child holds the spoon as
how he would with any natural object. When a parent intervene and
reorganize the handling to conform to a more social use, the child
develops the same ability that is to hold the spoon in the right
manner as how it should be. The development of this new ability cannot
be solely explained by the child’s internal genetic play but rather
environmental factors, here, role of parent came to play to influence
this acquisition of ‘cultural tool’. Vygotsky’s theory of social
constructivism highlights the importance of cooperative-learning
activities and interventions for ‘thought sharing’ so that the child
can acquire these tools when he interacts socially with his peer mates
or parents. He believed that relationship between the child and others
is a dynamic, interactional one. The child’s mind is not passive and
contains models of prior experiences which clash with patterns
currently internalized. The result of interaction with others will be
the birth of original ideas and creative contributions outstripping
those produced on the biological level alone.

Gardner (1993) defined ‘intelligence’ as the ability or skill to solve
problems or to fashion products which are valued within a cultural
setting. A child’s intelligence is not solely determined by genetic
model and is currently assumed to be subject to both genetic and
environmental influences. Evidence of genetic influence on
intelligence is grounded in twin and adoption studies (Plomin, 1994,
Plomin & Petrill, 1997, Steen, 1996). For example, correlation between
scores of monozygotic twins reared together is higher (approximately
.85) than correlations of dizygotic twins and less closely related
siblings (Plomin & Petrill, 1997). Environment, too, includes a broad
array of effects on intelligence; some influence whole populations
while others contribute to individual differences. These influences
include biological as well as social and cultural factors. A
biological factor such as prolonged malnutrition during childhood has
negative long-term intellectual effects. Exposure to lead can have a
negative effect on intelligence: Neisser et al. (1996) administered IQ
tests to children with high blood lead levels throughout childhood,
and found they scored substantially lower. Social and cultural aspects
of environment may influence intelligence. Schools promote the
development of intellectual skills such as systematic problem-solving,
abstract thinking, and categorization; children who attend regularly
may be expected to benefit more than those who attend sporadically. In
Scarr and Weinberg’s study (1983) of adoptive and biologically related
families with children between 16 and 22 years of age, they found
environment more powerful in influencing IQ level in the young child
than the young adult. They argue that better schooling, nutrition,
health care and psychological services can raise the level of
intellectual development.

In conclusion, the developing child is an active confluence between
genetic and environmental influences and represents a centre of
organization and creative potential of new response functions for his
development in his own right. A child is capable in inventing new
potential dimension for development free from the clutches of
pre-determinations in either environments or genes.

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