The Processes by Which Genes and Environment Interact to Influence Development

The Processes by Which Genes and Environment Interact to Influence Development
?Genes? refers to units of heredity information that consist of dna and are located on chromosomes and can exist in alternative forms called alleles (http://biology.about.com/library/glossary/bldefgenes.htm). ?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 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 led. 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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