The importance of being different.
The DNA of each individual is located in 22
pairs of homologous (similar; ‘autosomes’), and
one pair of non-homologous (dissimilar; ‘sex
determining’) chromosomes, which are
identically located in the nuclei of each cell
of the human body. At the time of conception,
each individual inherits a particular, set (the
genome) of pairs of constituent parts of
the DNA molecule (genes) – one of each
pair has been randomly chosen from one or
other of their two parents. The genes are each
found at a position (a locus) on a
chromosome. Each gene pair predisposes
(that is, has the potential) for the development
– or an aspect of the development – of a
particular trait – feature, process or behavior.
However, before the final expression
of a gene (that is, its manifestation in an
individual), it is subject to interaction with
any of the long, complex series of features, to
which it is exposed in the course of its
conception-to-death environments. These include:
internal – other genes, chemicals; and external
– personal, social, cultural, or any of the
other, vast diversity of other life experience
to which individuals are exposed. From these
interactions the end result of a gene pair may
be modifications to its predisposed trait – or
even to its being completely turned on or
off. Of special note are the early years’
imprinting of individual backgrounds with regard
to:, parents, society, environment and culture,
even economic status.
The importance of comprehending this complex
process, starting from random, gene selection
from each of their parents – and the many
events, which can later influence that
potential, is that:
Each human being is unique in their
particular combination of physical,
physiological and behavioral features.
As a result, between the millions of living
individuals, there is the vast range of
different attitudes, attributes and skills,
essential for the multiple, diverse activities
necessary in modern societies. But, in addition
to creating those basic individual
personalities, understanding genetic mechanisms
provides the necessary background for
appreciating the potential: for producing
medicines, of stem cell research, genetic
engineering, genetic fingerprinting, and much
more (50Genetics Ideas you
really need to know, Mark Henderson, 2008).
The modes of processes and actions of genes
and gene pairs are subject to an essentially
simple – but in practice quite complex – set of
genetic, chemical and mathematical, principles
and rules. As one, basic example of the system,
the gene for a particular trait might be
dominant or recessive, which means
that if both genes in a pair are
dominant, or even only one, the trait
will be manifested, if both are recessive, the
trait will not appear in the individual.
This aspect of biological inheritance is the
significant starting point for
appreciating in humans, the structures,
functions and behaviors of living, breathing
active individuals, and so, on averages, those
attributed to populations of people.
However, before the final expression
of a gene (that is, its manifestation in an
individual), it is subject to interaction with
the complex series of features, to which it is
exposed in the course of its conception-to-death
environments: internal, other genes, chemicals,
and external personal, cultural, social and
other life experiences. These exposures of a
gene or gene pair may result in modifications to
its predisposed trait or even to its being
turned on or off.
The environmental influences on different
traits vary greatly. As a generalization, in
physical (say, eye pigmentation) and
physiological (such as, blood groups) traits the
genetic basis is generally the determining
factor, but in aspects of behaviors, aptitudes
and intellect, the environmental encounters may
be highly significant. The early imprinting of
behaviors, including language, from early
family, cultural, economic and physical
environment is generally strong.
When viewing groups of people, of all sizes
and of the very many different types, the
individual differences constitute the population
variation. If the aspect is continuous,
such as for stature or pigmentation, there is an
average (mean value), with the range in the
population to various degrees greater or less,
forming what is called a normal curve,
with progressively less individuals on the
‘greater’ and ‘lesser’ sides. For
discontinuous (present or absent)
characteristics, for example for blood groups,
there is a range for each of the four types (O,
A, B, AB).