Heredity
All human beings are more or less alike with each
other in physical aspect. They vary considerably though in such factors as
height, color of the skin, facial characteristics and intelligence. How can we
seem to be alike but also be different at the same time? We all have the same
body parts but we are also different with each other. We are unique in our own
way because we have different genes that we inherited from our parents. You
inherited your height from your father while the color of your hair was inherited
from your mother. That’s why at the same time, the genes of your parents were
transferred to you. The reason behind this was the heredity.
Why do children look like their parents? Why do
brothers and sisters resemble each other? This is because we “inherit” traits
from our parents. The passing of traits from parents to child is the basis of
heredity. When we talk about heredity, the traits of one people can be relate
to it easily. Our genes encode the instructions that define our traits. Each of
us has thousands of genes, which are made of DNA and reside in our chromosomes.
The environment we grow up and live in also helps define our traits. For
example, while a person’s genes may specify a certain hair color, exposure to
chemicals or sunlight can change that color.
Humans have two complete sets of twenty-three
chromosomes, meaning forty-six in total.
These are threadlike structures that come in twenty-three pairs, one member of
each pair comes from one parent. These are composed of DNA or Deoxyribonucleic
Acid that is a complex molecule that contains genetic information. The units of
hereditary information are short segments of chromosomes that compose the DNA
that are known as genes. When parents conceive a child, they each contribute
one complete set to the child. In this way, parents pass genes to the child.
Twenty-two pairs of chromosomes carry genes that
determine the structures and behavior that are not sex-linked. The remaining
pair of chromosomes called the sex chromosomes determine the sex of an
individual. The sex chromosomes also carry genes determining other
characteristics called sex-linked characteristics like baldness, colorblindness
and hemophilia. By convention, the sex chromosomes are labelled x and y. Males
have an x and a y sex chromosomes, females have two xx chromosomes.
The genes are the hereditary factors or
“determiners” within the chromosomes. They are assumed to be “packets of
chemicals” strung along the chromosomes like beads on a thread or peas in a
pod. Studies reveal that one constituent
of genes, DNA has been tentatively identified as the primary genetic
substance.
Genes work in pairs because the chromosomes
inherited from the mother and the father pair up in such a way that pairs of
similar genes determine particular characteristics. If a trait is determined by
a single pair of identical genes, there is no doubt about the characteristics
that will be produced.
The similarities between organisms of any kind are
determined by heredity. Children are like their father or their mother or both.
Yet, even if children are much like their parents, they may also have some of
the characteristics of their grandparents. The reason behind this was because
we inherit not only from our parents but from our ancestors as well.
Even if children look very much like their
parents, we can still recognize one from each other. Each one of us tends to be
different from our parents and from one another. No two individuals are exactly
alike. Even identical twins differ from each other in certain ways. Some of
these differences between organisms of the same specie are due to heredity,
other are due to environment.
Every individual is a product of both heredity and
environment. Man is a product of both nature and nurture – under the influence
of these two factors he grows and changes biologically and psychologically.
Heredity and environment in interacting with one another produce the whole
range of individual differences.
Individuals differ from each other. Heredity and
environment produce the whole range of individual differences among human
beings. The internal environment is within an organism while the external
environment which the stimuli is from the outside. It also includes our social
environment composed of all human beings influencing us in any way or another.
Our social environment is extremely important in shaping our individual
especially our individual behavior and personality.
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