Heredity:

An individual has a specific set of limits which are the result of his biological heredity from parents or fore fathers.

This called heredity the term ‘heredity’ may also be used in another sense, for example, if a child is brought up in a particular social environment say of a tribe, the value of that tribe arid the norms of that tribe are inculcated in him through other members of that social group and we call it social heredity.

In the same way, a student in a classroom situation brings with him a specific cultural heredity also. Here in this”5ection our discussion will be focused on the influence of only biological heredity on individual differences. Each individual has a specific set of potentials which are developed through the environment.

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These potentialities and characteristics possessed by the individual are the result of his biological heredity. The influence of heredity is so strong that twins brought up in drastically different environment show very much similarity in terms of their mental abilities and other traits. This shows that even drastically different environments are not capable of overcoming heredity influences.

Genetic Basis of Individual Differences:

Generally when we talk about heredity, we invariable mean genes received by the individual from his parents at the time of conception. These combinations of genes are called chromosomes. Similar chromosomes form pairs and very similar to each other in terms of appearance and characteristics.

Each human cell contains 23 pairs of chromosomes, which may be seen only with the help of high powered microscopes. Each individual, at the time of conception is in the form of a single cell divided into two daughter cells which again divide themselves.

This process of division ultimately results in a matured organism. At the time of division, each cell has two identical sets of chromosomes resulting in identical heredity. Which cell will develop into a skin cell and which one into a bone cell depends upon the cellular environment? Genes of the individual interact with this cellular environment in different ways during the process of specialized development of different cells.

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A different type of cell division takes place when the individual attains sexual maturity. This process is called meiosis. Meiosis involves two cell divisions, during which the chromosome number is halved.

Reasons for Difference:

Individual differences are the result of a number of possible combinations of genes. In this system even a simple looking and small characteristic is the result of various genes. As is apparent, individual germ cells of each parent and those of two parents i.e. mother and father have a number of possible combinations of genes.

As a result, we find individual difference between two siblings. Since identical twins develop from the division of a single fertilized ovum, they are identical in terms of heredity. Physical characteristics are a result of heredity. Various physical characteristics i.e. colour of hair, eye, skin, etc. are the result of various combinations of genes.

If an individual receives two genes of albinism from the parents, the person will be an albino. Such an individual will be called homozygous. If the individual gets albinism from one parent and normal colorings from another, he will be called heterozygous. Since normal colorings are dominant such individual will have normal colorings.

Determination of Sex:

Likewise the sex of the individual is determined by the pair of chromosomes received from the parents. When the individual receives X chromosome from both the parents, the sex will be female.

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But if the individual receiver X chromosome from the mother and Y chromosome from the father, the sex will be male. Certain genes received by the individual through X chromosome result in sex-related characteristics.

Diseases:

A female receiving one dominant gene of hemophilia i.e. colour blindness from one parent and one normal gene from another parent is not likely to. Have this disease.

The reason is the normal gene will dominate the homophiles gene. In the case of a male, if a dominant hemophiliacs gene is passed on to the individual by the mother, the individual is likely to have this disease as the Y chromosome of father will not carry this gene at all.

Heredity and Mental Development:

Watson claimed to train any healthy child into someone expected or desired. The experiments on animal breeding proved that some kind of mental ability could be inherited. The early experiments on rats were conducted by Tryon (1942) at the University of California and by Heron (1935) at the University of Minnesota.

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They studied wide differences in maze learning (finding a way to a cheese through a maze) done by various groups of rats. They studied the ability to learn maze over generations after generations and it was found that with each generation the groups drew further apart.

Many psychologists interpreted these characteristics of rats as analogous to human intelligence. When these bright and dull rats were exposed to other learning problems, it was found that bright rats were not good at everything. Searle – Searle (1949), found that rats from each group showed a characteristics pattern of high or low scores which were quite different for each group.

It was found that the bright animals were characteristically food drivers, economical of distance, low in motivation of escape from water and timid in response to open spaces. The dull rats were better in water motivation and timid of mechanical apparatus features.

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Arthur Jensen:

Arthur Jensen of the University of California at Barely found that white children were genetically superior to black children. This argument claims that I.Q. has an extremely high genetic factor (about 80%) and that there must therefore, be racial differences in intelligence.

This study was later on criticized by many researchers. Jensen based his argument on the concept of hereditability. Since I.Q. is the result of heredity, environment and critical period (kajal), the hereditability value for I.Q. lies somewhere between 0 to 1.00. Jensen has argued that the actual value is somewhere near 80.

Since the teachers often treat black children as if they were devoid of intellectual resources, the children begin to fulfill his expectation by achieving less and less as the school years go by. One of the reasons for this drop relates to the placement of the least competent teachers in these schools.

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It is found that black children often do not progress beyond the (viii) or (ix) grade level. Its reason may be that the level of their teacher’s (non) competence does not help them beyond that point. One study found that two-thirds of the teachers tested stood lower than junior high school level on a proficiency test.