INTRODUCTION TO GENETICS biology

INTRODUCTION TO GENETICS biology
A feature of students’ attitude to Genetics is that it is a very difficult course, which
one takes only because it is compulsory. Some students reinforce this negative
attitude by the rationalization that they do not intend to do post-graduate work in
Genetics. These attitudes are not deceptively correct because they make you neglect
some of the more important aims of education. If you avoided the challenge posed by
some courses, you would be denying your intellect the stimulation it needs to spur it
to greater heights.
Besides, for a long time, Nigerian secondary school students have been denied
adequate exposure to Genetics because some people avoided the challenge. Genetics
is a vital aspect of everyday life and of Biology, and no biologist, regardless of his
level or interest, should avoid a meaningful exposure to it.
Dobzhansky, aptly summarizes the need for a broad exposure as follows:
“The advancement of science is, in the main, the business of
specialists. And as science expands, the specialists tend to
become narrow specialists. Some specialists have become
disgustingly narrow. Narrow specialists are ENDANGERED
and DANGEROUS (emphais mine) – endangered because
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their own inner lives are impoverished; dangerous because
they are liable to be easy prey for exploitation by those with
power or with money, for purposes inimical to both science
and to the interests of mankind as a whole … There should
exist, however, scientists able and willing now and then to
abandon the protective shells of their specialties, and to
engage in surveying broad vistas … people at large will have
their inner life enriched if they gain an appreciation of what
science and scientific attitude really are. Some aspects and
achievements of science are everyone’s
business” (Dobzhansky, 1964).
It is hoped that at the end of the course, you would have gained an understanding of
the principles governing the transmission of hereditary traits. All societies are
interested in understanding how certain traits are inherited in living things, including
man.
The puzzle about genetic inheritance in man is perhaps most succinctly expressed in
this portion of a poem by Aldous Huxley’s “Fifth philosopher”:
A million million spermatozoa
All of them alive;
Out of their cataclysm but one poor Noah
Dare hope to survive
And among that billion minus one
Might have chanced to be
Shakespeare, another Newton, a new Donne
But the One was Me
Why was that one me? Why do normal parents produce an albino and short parents
a tall child, or tall parents a short child? It is important for our well-being that we
should be able to answer simple questions about heredity without resorting to “old
wives tales”. But Genetics is not solely concerned with man, it is of great importance
in agriculture.
It is further hoped that at the end of this course, you will be able to appreciate the
fact that:
“Increased knowledge of heredity means increased power of control over the
living things, and as we come to understand more and more the architecture
of the plant or animal we realize what can and what cannot be done towards
modification or improvement …
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It is not, however, in the economic field, important as this may be, that Mendel’s
discovery is likely to have most meaning for us: rather it is in the new light in which
man will come to view himself and his fellow creatures, if it is shown that the
qualities of man, his body and his intellect, his immunities and his disease, even his
very virtues and vices, are dependent upon the ascertainable presence or absence of
definite unit-characters (genes) whose mode of transmission follows fixed laws, and
if also man decides that his life shall be ordered in the light of this knowledge, it is
obvious that the social system will have to undergo considerable changes” (Punnett,
1910).
This course deals with the basic principles governing heredity. Examples are chosen
merely to illustrate these principles. To that extent therefore, you will not be
expected to memorize examples, which may be new to you. This approach is dictated
not only by the fact that the basic laws of heredity are applicable to most
organizations, but also by the belief that with a good understanding of the principles
one can make extrapolations to explain particular situations.
Much of the difficulty, which students have with Genetics stems from the fact that
they had been used to purely descriptive aspects of biology. Genetics on the other
hand largely entails logical reasoning based on a number of interdependent principles
often involving some calculations. These calculations are within the scope of anyone
who has studied elementary mathematics.
Genetics is a course which demands alertness and consistent work in the forms of
reading and practice.
A note of warning should be sounded here: You would be deceiving yourself and
also doing yourself a disservice, if you merely read genetics as literature. It indeed
entails practicing on questions that boarder on the principles and laws of genetics.
You will have to work examples typifying these principles and laws to have the
concepts of genetics running in your blood.
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