DETERMINISM, REDUCTIONISM, AND GENETICS

One of the fundamental aspects of most Western science is reductionism. The idea,
attributed generally to influential thinkers such as Descartes and Francis Bacon,
derives from our notions of empirical experimental design that the phenomena of
nature can—indeed, perhaps should—be studied and understood part by part,
ultimately all the way down to the most fundamental parts. This does not mean
that each part acts independently, nor that we necessarily ever will understand all
aspects of a trait.

"Changes in DNA" - Color Atlas of Genetics, Eberhard Passarge

When it was recognized that changes (mutations)

in genes occur spontaneously (T. H. Morgan,

1910) and can be induced by X-rays (H. J.

Muller, 1927), the mutation theory of heredity

became a cornerstone of early genetics. Genes

were defined asmutable units, but the question

what genes and mutations are remained. Today

we know that mutations are changes in the

structure of DNA and their functional consequences.

The study of mutations is important

for several reasons. Mutations cause diseases,

including all forms of cancer. They can be induced

by chemicals and by irradiation. Thus,

they represent a link between heredity and environment.

And without mutations, well-organized

forms of life would not have evolved.

The following two plates summarize the chemical

nature of mutations.

"Biochemical polymorphism" - Color Atlas of Genetics, Eberhard Passarge

Biochemical polymorphism is detected by
laboratory methods. It results from individual
differences in the sequences of nucleotide bases
of DNA. If a difference leads to a change in a
codon, a different amino acid may be incorporated
at the corresponding site of the protein.
This can be demonstrated by analyzing the gene
product.
Subtle differences in the many biochemical reactions
between individuals was recognized
early last century as the basis of genetic individuality
by Archibald Garrod (Bearn, 1993).

"polymorphism" - Color Atlas of Genetics, - Eberhard Passarge

Genetic polymorphism is the existence of variants
with respect to a gene locus (alleles), a
chromosome structure (e.g., size of centromeric
heterochromatin), a gene product (variants in
enzymatic activity or binding affinity), or a
phenotype. The term DNA polymorphism refers
to a wide range of variations in nucleotide base
composition, length of nucleotide repeats, or
single nucleotide variants. DNA polymorphisms
are important as genetic markers to identify
and distinguish alleles at a gene locus and to determine
their parental origin.

"DNA polimorphism" - Color Atlas of Genetics, Eberhard Passarge

Genetic polymorphism is the existence of variants
with respect to a gene locus (alleles), a
chromosome structure (e.g., size of centromeric
heterochromatin), a gene product (variants in
enzymatic activity or binding affinity), or a
phenotype. The term DNA polymorphism refers
to a wide range of variations in nucleotide base
composition, length of nucleotide repeats, or
single nucleotide variants. DNA polymorphisms
are important as genetic markers to identify
and distinguish alleles at a gene locus and to determine
their parental origin.

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