What is Life? (Chapter 3) - Schrodinger, "Mutations"

Persons

Hugo Marie de Vries – was a Dutch botanist and one of the first geneticists. He is known chiefly for suggesting the concept of genes, rediscovering the laws of heredity in the 1890s while apparently unaware of Gregor Mendel’s work, for introducing the term “mutation”, and for developing a mutation theory of evolution.

Gregor Mendel – was a biologist, meteorologist, mathematician, Augustinian friar and abbot of St. Thomas’ Abbey in Brünn (Brno), Margraviate of Moravia.

Definitions

allele – one of two or more alternative forms of a gene that arise by mutation and are found at the same place on a chromosome.

homozygous – having two identical alleles of a particular gene or genes.

heterozygous – having two different alleles of a particular gene or genes.

phenotype – the set of observable characteristics of an individual resulting from the interaction of its genotype with the environment.

genotype – the genetic constitution of an individual organism.

Survival of the Fittest and Natural Seleciton

Darwin’s theory of sequential, continuous, and small variations is incorrect when it comes to how natural selection works.  If you plot variation in crops you will see variance in the form of a statistical bell curve with deviations from the mean on either side.  If you take a sample of above average size corn from a pure-bread strain and make a new crop, it will create a statistical curve identical to the original.  

Small continuous variations are not inherited.

Occasionally a “jump-like” change, or mutation, occurs.  In this instance there are no intermediate forms.  This is similar to quantum theory in which no intermediate energies occur between two neighboring energy levels.  These mutations are inherited. 

**note: a rule in quantum theory states small systems can only possess specific amounts of energy.  For this system to increase energy it must make a “quantum” jump to the next level without passing through an intermediate quantity of energy in between.   

**note: a quantum leap is a discontinuous transition between quantum states. What this means is that an electron in one energy level in an atom jumps instantly into another energy level, emitting or absorbing energy as it does so. There is no in-between state, and it doesn’t take any time for the leap to occur.

For Schrodinger, mutation can substitute Darwin’s slight variation to support natural selection.  In light of this, it would be wrong to say that the original version is orthodox and the mutant version is a heretic.  

Because two organisms look alike (phenotype) does not mean they differ in inheritance (genotype).

**A recessive allele influences the phenotype only when the genotype is homozygous.

Because some mutations are recessive, even detrimental mutations may not manifest because they are latent.  In this sense close breeding has harmful effects.

In order for mutations to be suitable for the work of natural selection, they must be rare events – else injurious mutations would dominate suitable ones negating natural selection.  (Example: in a manufacturing plant, improvements should be tried one at a time while keeping everything else constant to determine if the change is in fact an improvement or not).

 

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