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
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reserved © 1997-2000 Chris Rutt
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