More on this book
Community
Kindle Notes & Highlights
How often do we still hear that quantum effects can have little relevance in the study of biology, or even that we eat food in order to gain energy?
(There is nothing over which a free man ponders less than death; his wisdom is, to meditate not on death but on life.)
Cogito ergo sum. DESCARTES
chromosome fibre
Suppose that you could mark the molecules in a glass of water; then pour the contents of the glass into the ocean and stir the latter thoroughly so as to distribute the marked molecules uniformly throughout the seven seas; if then you took a glass of water anywhere out of the ocean, you would find in it about a hundred of your marked molecules.
Only in the co-operation of an enormously large number of atoms do statistical laws begin to operate and control the behaviour of these assemblées with an accuracy increasing as the number of atoms involved increases. It is in that way that the events acquire truly orderly features. All the physical and chemical laws that are known to play an important part in the life of organisms are of this statistical kind; any other kind of lawfulness and orderliness that one might think of is being perpetually disturbed and made inoperative by the unceasing heat motion of the atoms.
This example shows what funny and disorderly experience we should have if our senses were susceptible to the impact of a few molecules only. There are bacteria and other organisms so small that they are strongly affected by this phenomenon. Their movements are determined by the thermic whims of the surrounding medium; they have no choice. If they had some locomotion of their own they might nevertheless succeed in getting from one place to another – but with some difficulty, since the heat motion tosses them like a small boat in a rough sea.
For our organs of sense, after all, are a kind of instrument. We can see how useless they would be if they became too sensitive.
The laws of physics and physical chemistry are inaccurate within a probable relative error of the order of 1/√n, where n is the number of molecules that co-operate to bring about that law – to produce its validity within such regions of space or time (or both) that matter, for some considerations or for some particular experiment.
You see from this again that an organism must have a comparatively gross structure in order to enjoy the benefit of fairly accurate laws, both for its internal life and for its interplay with the external world.
Das Sein ist ewig; denn Gesetze Bewahren die lebend’gen Schätze, Aus welchen sich das All geschmückt.1 GOETHE
Thus we have come to the conclusion that an organism and all the biologically relevant processes that it experiences must have an extremely ‘many-atomic’ structure and must be safeguarded against haphazard, ‘single-atomic’ events attaining too great importance.
As we shall presently see, incredibly small groups of atoms, much too small to display exact statistical laws, do play a dominating role in the very orderly and lawful events within a living organism.
chromosomes, which number 8 or 12 or, in man, 48.
For though the single chromosomes are sometimes clearly distinguished and individualized by shape and size, the two sets are almost entirely alike. As we shall see in a moment, one set comes from the mother (egg cell), one from the father (fertilizing spermatozoon). It is these chromosomes, or probably only an axial skeleton fibre of what we actually see under the microscope as the chromosome, that contain in some kind of code-script the entire pattern of the individual’s future development and of its functioning in the mature state.
on the average as few as 50 or 60 successive divisions suffice to produce the number of cells4 in a grown man
Thus, a body cell of mine is, on the average, only the 50th or 60th ‘descendant’ of the egg that was I.
The drone has no father!
Every man6 owes just half of his inheritance to his mother, half of it to his father.
We have just introduced the term gene for the hypothetical material carrier of a definite hereditary feature.
a gene contains certainly not more than about a million or a few million atoms.
Being is eternal; for laws there are to conserve the treasures of life on which the Universe draws for beauty.
Und was in schwankender Erscheinung schwebt, Befestiget mit dauernden Gedanken.1 GOETHE
We know definitely, today, that Darwin was mistaken in regarding the small, continuous, accidental variations, that are bound to occur even in the most homogeneous population, as the material on which natural selection works. For it has been proved that they are not inherited. The fact is important enough to be illustrated briefly. If you take a crop of pure-strain barley, and measure, ear by ear, the length of its awns and plot the result of your statistics, you will get a bell-shaped curve as shown in Fig. 7, where the number of ears with a definite length of awn is plotted against the
...more
This highlight has been truncated due to consecutive passage length restrictions.
The mutations are actually due to quantum jumps in the gene molecule.
They are supposed to be non-relatives, free of the mutation.
Recessive mutations are even more frequent than dominant ones and are very important, though at first they do not show up at all.
heterozygous,
homozygous.
The fact that two individuals may be exactly alike in their outward appearance, yet differ in their inheritance, is so important that an exact differentiation is desirable. The geneticist says they have the same phenotype, but different genotype.
A recessive allele influences the phenotype only when the genotype is homozygous.
Next to self-fertilization (only possible in hermaphrodite plants) the greatest danger would be a marriage between a son and a daughter of mine. Each of them standing an even chance of being latently affected or not, one-quarter of these incestuous unions would be dangerous inasmuch as one-quarter of its children would manifest the damage. The danger factor for an incestuously bred child is thus 1:16.
This is perhaps the place for a word on the early history of genetics. The backbone of the theory, the law of inheritance, to successive generations, of properties in which the parents differ, and more especially the important distinction recessive-dominant, are due to the now world-famous Augustinian Abbot Gregor Mendel (1822–84).
Mendel knew nothing about mutations and chromosomes. In his cloister gardens in Brünn (Brno) he made experiments on the garden pea, of which he reared different varieties, crossing them and watching their offspring in the 1st, 2nd, 3rd, …, generation. You might say, he experimented with mutants which he found ready-made in nature. The results he published as early as 1866 in the Proceedings of the Naturforschender Verein in Brünn. Nobody seems to have been particularly interested in the abbot’s hobby, and nobody, certainly, had the faintest idea that his discovery would in the twentieth
...more
In order to be suitable material for the work of natural selection, mutations must be rare events, as they actually are.
An analogy might be sought in the working of a large manufacturing plant in a factory. For developing better methods, innovations, even if as yet unproved, must be tried out. But in order to ascertain whether the innovations improve or decrease the output, it is essential that they should be introduced one at a time, while all the other parts of the mechanism are kept constant.
And what in fluctuating appearance hovers, Ye shall fix by lasting thoughts.
Und deines Geistes höchster Feuerflug Hat schon am Gleichnis, hat am Bild genug.1 GOETHE
In this case it is supplied by quantum theory. In the light of present knowledge, the mechanism of heredity is closely related to, nay, founded on, the very basis of quantum theory. This theory was discovered by Max Planck in 1900.
Thus the births of the two great theories nearly coincide, and it is small wonder that both of them had to reach a certain maturity before the connection could emerge.
And thy spirit’s fiery flight of imagination acquiesces in an image, in a parable.
Sane sicut lux seipsam et tenebras manifestat, sic veritas norma sui et falsi est.1 SPINOZA, Ethics, Pt II, Prop. 43.
Are there really no other endurable structures composed of atoms except molecules?
C2H6O + 3O2 = 2CO2 + 3H2O,
We believe a gene – or perhaps the whole chromosome fibre3 – to be an aperiodic solid.
Truly, as light manifests itself and darkness, thus truth is the standard of itself and of error.
Nec corpus mentem ad cogitandum, nec mens corpus ad motum, neque ad quietem, nec ad aliquid (si quid est) aliud determinare potest.1 SPINOZA, Ethics, Pt III, Prop.2
What an organism feeds upon is negative entropy. Or, to put it less paradoxically, the essential thing in metabolism is that the organism succeeds in freeing itself from all the entropy it cannot help producing while alive.
entropy is measured is cal./°C
How would we express in terms of the statistical theory the marvellous faculty of a living organism, by which it delays the decay into thermodynamical equilibrium (death)?
