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010 - Radiation Ionizing Radiation · Percheron horse

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  Speaker 1: Section nine of the Genetic Effects of radiation. This is
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  Speaker 1: a LibriVox recording. All LibriVox recordings are in the public domain.
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  Speaker 1: For more information or to volunteer, please visit libyvox dot
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  Speaker 1: org wed by Yoganan, Genetic Effects of Radiation by Isaac
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  Speaker 1: Asimov and Theodosius Dobzanski Radiation ion acing radiation a modern
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  Speaker 1: technological civilization exposes mankind to two general types of genetic
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  Speaker 1: dangers unknown earlier synthetic chemicals or unprecedentedly high concentrations of
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  Speaker 1: natural ones absent in earlier eras, and intensities of energetic variation.
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  Speaker 1: Equally unknown or unprecedented chemicals can interfere with the process
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  Speaker 1: of replication by offering alternate pathways with which the cellular
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  Speaker 1: missionary is not prepared to cope. In general, however, it
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  Speaker 1: is only those cells in direct contact with chemicals that
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  Speaker 1: are so affected, such as the skin, the intertinal linings,
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  Speaker 1: the lungs, and the liver, which is active in altering
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  Speaker 1: and getting rid of foreign chemicals. These may undergo somatic mutations,
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  Speaker 1: and an increased incidence of cancer in those tissues is
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  Speaker 1: among the drastic results of exposure to certain chemicals. Such
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  Speaker 1: chemicals are not, however, likely to come in contact with
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  Speaker 1: the gonads where the sex cells are produced. While individual
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  Speaker 1: persons may be threatened by the manner in which the
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  Speaker 1: environment is being permeated with novel chemicals, the next generation
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  Speaker 1: is not affected in advance. Radiation is another matter in
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  Speaker 1: its broadest sense, variations any phenomena spreading out from some
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  Speaker 1: swords in all directions. Physically, such radiation may consist of
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  Speaker 1: waves or of particles. Footnote. Actually, all waves have some
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  Speaker 1: of the characteristics of particles, and all particles have some
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  Speaker 1: of the characteristics of waves. Usually, however, the radiation is
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  Speaker 1: predominantly one or the other, and little confusion arises under
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  Speaker 1: the ordinary circumstances in space, speaking of waves and particles
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  Speaker 1: as though they were separate phenomena. End of footnote. Of
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  Speaker 1: the wave forms, the two best known, or sound and
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  Speaker 1: electromagnetic variations. Sound carries very low concentrations of energy. This
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  Speaker 1: energy is absorbed by living tissue and converted to heat.
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  Speaker 1: Heat in itself can increase the mutation rate, but the
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  Speaker 1: effect is a small one. The body is effective machinery
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  Speaker 1: for keeping its temperature constant, and the gonads are not
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  Speaker 1: likely to suffer unduly from exposure to heat. Electromagnetic variation
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  Speaker 1: comes in a wide range of energies, with visible light
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  Speaker 1: the best known example of such variation because we can
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  Speaker 1: detect it directly and with great sensitivity. About in the
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  Speaker 1: middle of the range. Electromagnetic variations less energetic than light,
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  Speaker 1: such as infrared waves and microwaves, are convertan to heat
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  Speaker 1: when absorbed by living tissue. Heat thus formed is sufficient
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  Speaker 1: to cause atoms and molecules to vibrate more rapidly, but
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  Speaker 1: this added vibration is not usually sufficient to pull molecules apart,
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  Speaker 1: and therefore does not bring up about chemical changes. Light
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  Speaker 1: will bring about some chemical changes. It is energetic enough
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  Speaker 1: to cause a mixture of hydrogen and chlorine to explode.
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  Speaker 1: It will break up silver compounds and produce tiny black
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  Speaker 1: graines of metallic silver. The chemical basis of photography. Living tissue, however,
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  Speaker 1: is largely unaffected great now, the eye being one obvious exception.
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  Speaker 1: Ultravolet light, which is more energetic than visible light, correspondingly
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  Speaker 1: can bring about chemical changes more easily. It will redden
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  Speaker 1: the skin, stimulate the production of pigment, and break up
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  Speaker 1: certain steroid molecules to form vitamin D. It will even
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  Speaker 1: interfere with replication to some extent. At least, there is
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  Speaker 1: evidence that persistent exposure to sunlight brings about heightened tendency
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  Speaker 1: to skin cancer. Ultravolet light is not very penetrating, however,
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  Speaker 1: and its effects are confined to the skin. Electromagnetic variation
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  Speaker 1: more energetic than ultravolet light, such as X rays and
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  Speaker 1: gama RaSE, carry sufficient concentrations of energy to bring about
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  Speaker 1: changes not only in molecules, but in the very structure
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  Speaker 1: of the atoms making up those molecules. Atoms consist of
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  Speaker 1: particles electrons, each carrying a negative electric charge. Atoms consist
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  Speaker 1: of particles electrons, each carrying a negative electric charge, and
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  Speaker 1: circling a tiny, centrally located nucleus, which carries a positive
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  Speaker 1: electric charge. Ordinarily, the negative charges of the electrons just
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  Speaker 1: balance the positive charge in the nucleus, so that atoms
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  Speaker 1: and molecules tend to be electrically neutral. An extraor gamma
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  Speaker 1: ray crashing into an atom will, however, jar electrons loose.
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  Speaker 1: What is left of the atom will carry a positive
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  Speaker 1: electric charge, with the charge size proportional to the number
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  Speaker 1: of electrons lost. An atom fragment carrying an electric charge
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  Speaker 1: is called an ion. X rays and gamma rays are
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  Speaker 1: there for examples of ionizing radiation. Radiations may consist of
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  Speaker 1: flying particles two and if these carry sufficient energy, they
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  Speaker 1: are also ionizing in character. Examples are cosmic rays, alpha rays,
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  Speaker 1: and beta rays. Cosmic rays are streams are positively charged nuclear,
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  Speaker 1: predominantly those of the element hydrogen alpha race as streams
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  Speaker 1: are positively charged helium nuclear beta race as streams have
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  Speaker 1: negatively charged electrons. The individual particles contained in these rays
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  Speaker 1: may be referred to as cosmic particles, alpha particles, and
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  Speaker 1: beta particles, respectively. Ionizing radiation is capable of imparting so
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  Speaker 1: much energy to molecules as to cause them to vibrate
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  Speaker 1: themselves apart, producing not only ions, but also high energy,
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  Speaker 1: uncharged molecular fragments called free radicals. The direct effect of
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  Speaker 1: ionizing radiation on chromosomes can be serious enough. Chemical bonds
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  Speaker 1: may be disrupted so that a chromosomes struck by higher
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  Speaker 1: energy wave or particle may break into fragments, even if
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  Speaker 1: the chromosome manages to remain intact. An individual gene long
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  Speaker 1: its length may be badly damaged and a mutation may
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  Speaker 1: be produced if only direct hits mattered variation effects would
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  Speaker 1: be less dangerous than they are, since such direct hits
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  Speaker 1: are comparatively few. However, neomess may also be deadly, as
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  Speaker 1: streaking bit of radiation may strike a water molecule near
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  Speaker 1: a gene and may break up the molecule to form
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  Speaker 1: a free radical. The free radical will be sufficiently energetic
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  Speaker 1: to bring about a chemical reaction with almost any molecule
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  Speaker 1: it strikes. If it happens to strike the neighboring gene
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  Speaker 1: before it has disposed off that energy, it will produce
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  Speaker 1: the mutation as surely as the original variation might have. Furthermore,
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  Speaker 1: ionizing variations, particularly off the electromagnetic variety, tend to be penetrating,
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  Speaker 1: so that the interior of the body is as exposed
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  Speaker 1: as is the surface. The gnats cannot hid from X rays,
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  Speaker 1: gamma rays of cosmic particles. All these variations can bring
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  Speaker 1: about somatic mutations, all can cause cancer. For instance, what
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  Speaker 1: is verse, All of them increase rate of genetic mutations
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  Speaker 1: so that their presence threatens generations and born as well
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  Speaker 1: as the individuals actually exposed. End of Section nine. Ionizing
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  Speaker 1: radiation