INFLUENCE

OF

HEREDITY

AND

ENVIRONMENT

INTRODUCTION All human beings are a product of HEREDITY

and ENVIRONMENT. Heredity and environmental factors together

play a vital role in shaping human beings.

Psychologists commonly refer to heredity as “NATURE” and environment as “NURTURE”.

ROLE OF HEREDITY

Heredity refers to our biologically inherited characteristics.

In common words heredity refers to characteristics that we get from our parents.

Our physical characteristics such as the color of the skin, shape of the nose, color of eyes are inherited from parents.

Besides influencing our physical characteristics, heredity also influences our “BEHAVIOUR”.

THE MECHANISM OF HEREDITY

The true beginning of human being is a “SINGLE SECOND EVENT.”

A human being is conceived when a single sperm (male reproductive cell) from the father’s body fertilizes the ovum (female reproductive cell or egg) from the mothers body to form a “Zygote.”

This process is called “Fertilization” in which a sperm and ovum combine to create a single cell called “Zygote.”

Which sperm meets which ovum is of critical importance as it will determine the sex, appearance and several other characteristics of the new life.

The sperm is one of the several million sperm cells produced in the father’s body and the ovum is one of the several thousands ova produced in the mother’s body.

CHROMOSOMES The zygote consists of 46

chromosomes, half from each parent.

That is the zygote receives 23 chromosomes from the father (sperm) and 23 from the mother (ovum).

Each chromosome contains “Thousands of Genes.”

This discovery is credited to “GREGOR MENDEL.”

GENES GENES are made of a

complex chemical substance called the DNA (Deoxyribonucleic Acid.)

Each gene has a different role to play.

They go on to become different structures of the human body from the skin, muscle and other tissues of the body such as heart, lungs, eyes etc..

The genes that we get from our parents are purely a matter of “Chance.”

This is the reason why two children of the same parents are so different (except in the case of identical twins.)

Studies have found that there is almost a 50% difference in the genes of Brothers and Sisters.

They are basic units of heredity.

Genes are structures present on the chromosomes.

Genes are only responsible for passing of heredity traits from one generation to another.

Hence, Genes are commonly known as “Carriers of Heredity.”

CLASSIFICATION OF GENES

GENES

Dominant Genes Recessive Genes

A) DOMINANT GENES

A gene whose effect shows up in a child, whether or not, it is paired with a similar type of gene is called a “Dominant Gene.”

For example, If a child receives a gene for blue eyes from the father and brown eyes from the mother, then the child will have ‘brown eyes.’ This is because, the gene for the ‘brown eyes’ is a dominant gene.

B) RECESSIVE GENES

A Recessive Gene is one whose effect shows up only and only when it is paired with one just like itself.

It will not reveal its characteristics when it is paired with a dominant gene.

For example, the gene for blue eyes is a recessive gene. It will express its characteristics only when it is paired with another gene for blue eyes.

DETERMINANTS OF THE SEX OF THE CHILD

The zygote consists of 46 chromosomes. These 46 chromosomes are arranged in 23

pairs. Out of these 23 pairs, the first 22 pairs are

called “Autosomes” or “Non-sex chromosomes.”

The 23rd pair is called the “Sex chromosome.” This pair determines whether the new human

being will be a male or a female.

Sex chromosomes are either “X” or “Y” chromosomes.

The ovum always contributes an X chromosome.

The sperm may contribute an X or a Y chromosome.

When the zygote formed is ‘XX’, a Female child will be born.

When the zygote formed is ‘XY’, a male child will be born.

Thus, the sex of the child depends entirely on the sperm whether it contributes an X or a Y chromosome.

And hence,“it is the father who is solely responsible for the sex of the child.”

But due to ignorance in our Indian Society, there is tremendous pressure on the woman to give birth to a male child.

This is indeed sad because it is the father’s sperm that determines a child’s sex.

TWINS

A) MONOZYGOTIC TWINS Monozygotic Twins

develop from a “Single Fertilized Egg.”

In the case of these twins, the zygote splits into “Two Halves.”

They are commonly known as “Identical Twins.”

They are of the same sex and look alike.

B) DIZYGOTIC TWINS Dizygotic Twins develop

from two separate zygotes.

They are commonly known as “Fraternal Twins.”

They are developed from different sperms and are ‘siblings’ born at different times.

They may or may not be of the same sex and they do not look alike.

ROLE OF THE ENVIRONMENT

The term “Environment” refers to all external events or conditions to which an individual is exposed.

It is the world or society in which we are born and brought up.

Environment includes both Prenatal and Postnatal conditions.

Prenatal conditions are before birth and Postnatal are after birth conditions.

Before birth, the individual develops in the environment of his mother’s womb.

So everything that happens to a woman during pregnancy can affect the child.

After birth, he is affected by the environment which consists of the outside world, family, school, peers and culture.

A) PRENATAL ENVIRONMENT

The “Prenatal Environment” refers to the environment before birth.

Some of the factors that affect the Prenatal Environment are:

i. Prenatal Nourishmentii. a) Drug Intake b) Smokingiii. Mother’s Healthiv. Medical X-raysv. Mother’s Agevi. Environmental Hazards

i. PRENATAL NOURISHMENT

Babies develop best when the mothers eat well.

A woman’s diet before as well as during pregnancy is crucial to her child’s future.

A pregnant woman should have a well balanced diet.

It must include proteins, dairy products, bread, cereals, and fruits and vegetables rich in Vitamin C.

ii. a) Drug Intake

Everything that a mother takes finds its way to a new life.

A pregnant woman must not take any medication without consulting a doctor.

Drinking alcohol can also harm the “Fetus.”

It can lead to Fetal Alcohol Syndrome (FAS).

FAS causes slow prenatal and postnatal growth.

b) Smoking

Smoking during pregnancy is the cause of poor fetal growth.

Pregnant smokers give birth to small babies.

Smoking during pregnancy can cause bleeding during pregnancy and death of the fetus or newborn.

iii. Mother’s Health Illnesses suffered by a pregnant woman can

have serious effect on the developing fetus.

How serious the effects are, depends on the level of sickness of the pregnant woman.

Sexually Transmitted Diseases (STD) and diseases such as measles can have terrible effects on the health of the baby.

iv. Medical X-rays Exposure to X-ray

radiations can cause gene mutations.

Gene mutations are minor changes that alter a gene to produce a new harmful characteristic.

Exposure to radiations should be avoided especially during the first three months.

v. Mother’s Age

A woman’s age at the time of pregnancy is also an important factor.

Older pregnant women are more likely to suffer complications.

There is a greater risk of miscarriage, premature delivery, retarded fetal growth to older women.

Women over the age of 35 are at the greatest risk.

vi. Environmental Hazards

Exposure to chemicals, radiations, extremes of heat and humidity can affect prenatal development.

Exposure to nuclear radiations are extremely dangerous.

It increases the risk of mental retardation and is the cause of smaller head size and chromosomal abnormalities.

Postnatal Environment

The postnatal environment refers to the environment after birth.

It is also known as “External Environment”. The postnatal environment can be broadly

classified into 3 areas:

i. Physical environment

ii. Social environment

iii. Cultural environment

i. Physical Environment

The physical environment into which an individual is born, has a significant impact on the individual’s growth and development.

The geographical conditions of the region also have an impact on an individual’s development.

The physical environment includes the availability of food, clothing and shelter. Poor nourishment and diet have negative effects on an individual’s height, weight, eyesight and even mental development.

ii. Social Environment

The social environment is the society in which an individual is born and brought up.

It includes the family, school, peers, neighborhood, to which an individual is strongly exposed.

The individual is strongly affected by the kind of experience he has in his social environment.

iii. Cultural Environment

Culture refers to customs and ways of behavior that are common to a society.

It is a society’s or a group’s total way of life.

It includes customs, traditions, beliefs, values, language, passed on from parents to children.

NATURE VERSUS NURTURE

Psychologists differ with regards to the importance they give to nature and nurture.

However in reality, both heredity and environment interact with each other to influence the development of the individual.

Heredity sets limits and environment helps the individual reach the limits.

Heredity factors produce their effects under the conditions provided by the environment.