Heredity

Patterns of behavior may be thought as being shaped three kinds of factors: heredity, maturation and learning. through the action between these factors. It is probably There is continuous interacting unwise to seek “Pure” examples of behavior, or those which are formed entirely through of inherited patter growth processes learning always plays some role, direct or indirect, in the formation of a sequence of new responses Structure always limits development and the range are important links between biological processes of possible behavior changes. There l within our bodies and many aspects Many aspects of our biological nature are inherited. of behavior.

HEREDITY/NATURE Heredity involves all those physiological and It explains why people differ a person inherits from his parents. Psychological characteristics which and why persons who are related resemble one another more than persons who are totally unrelated. Heredity covers all the factors that were present in the individual when he began his life (not at birth but at the time of conception).

Heredity determines facial features etc. Heredity the structure, color of the skin, the color of hair, height, is the potential each person receives from his or her parents through transmission of genes. According to Ruch, Heredity is defined as the totality of biologically transmitted factors that influence the structure of body.

Genetic influences on the foetus

In 95 to 98 percent of cases there is normal development of foetus but in remaining 2 to 5% of cases, children are delivered with serious birth defects. A major cause of such defects is genetic—the information in the chromosomes in herited from one or both of parents causes  a problem.

Most common genetic defects are-
1. Phenyl Ketonuria (PKU). An inherited disease that prevents its  victims from being able to produce an enzyme that resists certain poisons, resulting in profound mental retardation.
2. Sickle-cell anaemia. It is a disease of blood which gets its name from the
abnormal shape of red blood cells. Children with such a disease may have poor appetite, swollen stomachs, and yellowish eyes and they rarely live beyond childhood.
3. Tay-Sach disease. It is a genetic defect preventing the body from breaking down fat and typically causing death by the age of 3 or 4. If both the parents carry the genetic defect producing the fatal illness, their child has one in four chances of being born with the disease (Havon and Proia, 1989).

4. Down Syndrome. It is a disorder caused by the presence of an extra chromosome, resulting in mental retardation. Down syndrome is related to the mother’s and father’s age; mother over 35 in particular, stand a higher risk of having a child with the problem.

Laws of Heredity

(a) Like begets like,
(b) Variation, and
(c) Regression.

(a) Like begets like

This principle states that the children have a tendency to be like their parents-like father, like son. The children of bright parents tend to be bright and those of dull tend to be dull. In the same way handsome parents tend to have handsome children, and ugly parents tend to have ugly ones. But, this law is not universally true. It has exceptions. Sometimes, we see that white parents have black children or bright parents have less bright children. Such occurrences can be explained by second law of inheritance known as “Law of Variation”.

(b) Variation

The children are not exactly like their parents. They have differences of features etc. The law of variation explains the causes of these differences in the children of the same family. It is due to the fact that germ-cells of the parents have genes which unite in various ways • and each combination produces a different quality of offspring. That is, there will be as many variations as there are possible combinations of genes.

We sometimes find that the same parents have children who are very different from one another. This is because of the different combinations of the genes of the same parents. Since our traits depend upon the combination of genes, the different combinations will give birth to different types of children e.g. one combination would produce a white child and the other a black.

(c) Regression

According to Sorenson, “The tendency for the children of very. bright parents to be less bright than their parents and a comparable tendency for the children of very inferior parents to be less inferior, is called regression.” The children of brilliant parents will tend to be of average intelligence. It is so, because every trait has a regressive tendency towards the average. It does not mean that regression always occurs; but the existence of such a tendency cannot be denied.