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Essential
Genetics for the Terrified
by Chris Rutt
Part 1: A
Beginning
There are three branches of
Genetics.
- First, and the area which
will mainly concern us, Transmission Genetics. We mate two
organisms with different characteristics and observe the transmission
of these traits to the next generation, and on into subsequent
generations. Scientific shorthand for "the next generation" is "F1". We
then mate the F1 organisms together (brother to sister1) and again observe the transmission of these
traits to the next generation, known as "F2". Because this was the
method used by a priest named Mendel, in the middle of the last
century, this is sometimes referred to as Classical or Mendelian
Genetics.
- The second branch, Molecular
Genetics, deals with the subject from the biochemical point of
view. I shall not be going into any detail of this field of study.
- The third branch, Population
Genetics, deals with the variation found within and among very
large groups, and although this branch of the science began at the
level of visible appearance or "phenotype2", much of the study is now done on the molecular variation
in a population. This leads on to how species are formed, and the
differences between them, but we have no need of this branch of
genetics in a basic introduction.
Before Abbot Mendel's work,
it was thought that parental characteristics blended in the offspring,
but Mendel realised that in many cases this was demonstrably untrue. He
did his work with peas, and many of the follow up studies (not done
until the early years of this century) were done with fruit flies. I
will however try to translate this work into Lovebird terms in the
belief that they will be more familiar to the reader and therefore more
understandable.
Mendel saw that a characteristic, such as feather colour, can occur in
a number of different forms. He used green and yellow peas, but had he
used Peachfaced Lovebirds, he would have made the observation from
practical experience that if you cross a pure Marine (a more modern
term for Pastel Blue. We should NEVER refer to these birds as "blue", a
colour which is still to be produced in this species) with a pure Light
Green, you do not get an intermediate colour, but one only, in this
case the light green.
From this he deduced that, rather than the parents' colours blending in
the young, each parent contributed its own colour by passing on some
"particle", which later became known as a "gene".
1For simplicity, brother to sister, father to
daughter, and mother to son mating are often used as examples. This is
of course bad practice from a practical point of view and an
understanding of genetics helps to explain why this is so.
2Another piece of scientific shorthand;
"phenotype" means the displayed characteristics of an individual. So,
if we consider one specific Lovebird, a Light Green (normal or wild
type) Peachfaced individual, "Light Green" is the "phenotype",
irrespective of the colours of its parents and other inheritable colour
characteristics that it may have.
Part 2: Dominance
All rights reserved
© 1997-2000 Chris Rutt
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