It is important to understand the factors that determine the course of development. Each one of us is a product of genetic factors and environmental influences.
At the time of conception, the ovum of the mother and the sperm cell of the father unite to form a new cell. The small particles in the nucleus of the cell are called chromosomes. The chromosomes exist in pairs. The human cell has 46 chromosomes arranged in 23 pairs.
One member from each pair comes from the mother and the other one from the father. Chromosomes store and transmit genetic information. The genes, which are the actual trait carriers, are found in very large numbers in each chromosome.
The fertilized zygote brings together various combinations of chromosomes. In this way, different genes are transferred from each child of the same set of parents. Due to this reason each child bears greater similarity to his on her blood relatives than to anyone else. At the same time there are also many differences amongst blood relatives.
Genotypes and Phenotypes
Genetic transmission is a complex process. Most characteristics that we observe in human beings are combinations of a large number of genes. Innumerable permutations and combinations of genes are responsible for the large differences in physical and psychological characteristics.
Only identical or monozygotic twins have exactly the same set of chromosomes and genes as they are formed by duplication of a single zygote. Most twins are fraternal or di-zygotic, who develop from two separate zygotes. These fraternal twins may resemble each other like brother and sister, but they will also be different from one another in many ways.
Genes can be dominant or recessive. There is more color blindness or lack of sensitivity to certain colors among males than females. A grandmother and mother can transmit this condition to the male child without being color blind themselves. This is because in the male this disorder is dominant, whereas in female it is recessive. The genes form pairs. If both genes in a pair are dominant, the individual will display the specific trait (e.g. color blindness). If one gene is dominant and the other recessive, the dominant will prevail. The recessive gene will be passed on and may show up in a later generation.
The dominant gene, therefore, is the one responsible for a particular trait to show up in a person. The characteristics which show up and are displayed e.g. eye color, are called phenotypes. The recessive gene does not show up as a trait, unless paired with another gene just like it. The characteristics that are carried genetically as recessive genes but are not displayed are called genotypes.
Genotype, therefore, refers to the actual genetic material or a person’s genetic heritage while phenotype refers to the individual’s physical and behavioral characteristics which are determined by both genetic and environmental factors.
Nature refers to what a child has inherited genetically from her parents, while the influence of environment on the development of the child is referred to as nurture. To understand the development of a person, we have to study the complex interaction between nature and nurture or heredity and environment.
Environmental influences are important both at the prenatal and postnatal stages of human development. At the prenatal stage, when a fetus is in the mother’s womb, internal or external harmful agents, such as certain legal or illegal drugs, alcohol, lead and pollutants can harm the unborn baby’s development. The mother’s nutrition, diseases and emotional stress can also affect the development of the fetus.
After birth, several types of environmental factors operate to influence the development of the child. The ecological systems theory of development views environmental factors organized as concentric circles of systems.
The micro-system is the immediate environment at home and interactions between them and the child’s own characteristics. The meso-system consists of the relationships between family members and school and neighborhood. The exo-system refers to the influences of indirect agencies such as work-place of the parents or community services.
The macro-system is the outermost layer which includes cultural values, laws and customs. The systems are ever-changing and dynamic. There is also a chronosystem which refers to the time dimension. As the child grows, there are changes within each system, and also changes due to the child’s interaction with the environment. On the whole, in ecological systems theory, children are both products and producers of their environments, in a network of interdependent effects.
The present view of development gives importance to both nature and nurture. Heredity and environment are inseparably interwoven, each affecting the impact of the other on the child. Development therefore has certain universal features, as well as features unique to the individual. It is important to understand the role of heredity, but more fruitful to understand how the environment can be improved, so as to help the child develop in the best possible way within the limits set by heredity.
An understanding of the principles and determinants of development helps us in several ways:
It helps us to know what to expect of the individual’s capability at a particular age.
It gives information on when to provide opportunities and stimulation for optimal development.
It helps to parents, teachers and others who work with children, to prepare them for the physical and psychological changes that are to take place.
It helps us to be prepared for changes in our bodies and personalities as we grow older.
It helps us to understand that it is possible to facilitate the process of development by providing an enriched environment.