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    GREGOR MENDEL (1822- 84)

    1865 – Austria

    • ‘Law of Segregation: In sexually reproducing organisms, two units of heredity control each trait. Only one of such units can be represented in a single sexually reproductive cell’

    • ‘Law of Independent Assortment: Each of a pair of contrasted traits may be combined with either of another pair’

    These laws laid the foundation for the science of genetics.

    The biologist Lamarck (1744-1829) had proposed a theory of inheritance of acquired characteristics and had suggested that inherited characteristics are influenced by environment. Mendel planted an atypical variety of an oriental plant next to a typical variety – the offspring retained the essential traits of their parents, which meant that the characteristics that were inherited were not influenced by the environment. This simple test led Mendel to embark on the path that would lead to the discovery of the laws of heredity.

    Mendel’s aim was to discover ” a generally applicable law of the formation and development of hybrids “. He addressed this by studying the effect of cross-breeding on seven pairs of contrasting characteristics of Pisum sativum, a strain of pea.
    His work on peas indicated that features of the plant; seed shape, seed colour, pod shape, pod colour, flower colour, flower position and stem length; were passed on from one generation to the next by some physical element. He realised that each characteristic of a plant was inherited independently, and that the ratios of plants exhibiting each trait could be statistically predicted.

    photograph of GREGOR MENDEL ©

    GREGOR MENDEL

    A common assumption in Mendel’s time was that when two alternative features were combined, an average of these features would occur. For example, a tall plant and a short one would result in medium height offspring. For seven years Mendel kept an exact record of the inherited characteristics of 28,000 pea plants, taking great pains to avoid accidental cross-fertilization; then he applied mathematics to the results. These quantitative data allowed him to see statistical patterns and ratios that had eluded his predecessors.

    From his analysis he found that certain characteristics of plants are due to factors passed intact from generation to generation.
    Mendel observed that individual plants of the first generation of hybrids (crossbred plants) usually showed the traits of only one parent. The crossing of yellow seeded plants with green seeded ones gave rise to yellow seeds; the crossing of tall stemmed ones with short-stemmed varieties gave rise to tall-stemmed plants.

    The factors determining a trait are passed on to the offspring during reproduction.

    Mendel worked out that the factors for each trait are grouped together in pairs and that the offspring receives one part of a pair from each parent.

    Contrary to the popular belief of the time, these factors do not merge. Any individual pea always exhibits one trait or the other, never a mixture of the two possible expressions of the trait; only one trait from each pair of factors donated by the parents would be expressed in the offspring, although there are four possible combinations of factors.
    This is now described as Mendel’s law of segregation.
    An offspring inherits from its parents either one trait or the other, but not both.

    He decided that some factors were ‘dominant’ and some were ‘recessive’ and was able to conclude that certain expressed traits, such as yellow seeds or tall stems, were the dominant ones and that other traits, such as shortness of stem and green seeds, were recessive. It appeared that the dominant factors consumed or destroyed the recessive factors – but this could not be the case, as the second generation of hybrids exhibited both the dominant and recessive traits of their ‘grandparents’. Across a series of generations of descendants, plants did not average out to a medium, but instead inherited the original features (for example, either tallness or shortness) in consistent proportions, a ratio of 3:1, according to the dominant factor.
    The 3:1 ratio would apply because the dominant factor would feature whenever it was present.

    He also noted that the different pairs of factors making up the characteristics of the pea plant ( such as the pair causing flower colour, the pair causing seed shape and so on ), when crossed, occurred in all possible mathematical combinations. This convinced him that the elements regulating the different features acted independently of each other, so the inheritance of one particular colour of flower was not influenced, for example, by the inheritance of pea shape.
    This is now described as Mendel’s law of independent assortment.

    He first articulated his results in 1865 and in 1866, which was shortly after Darwin’s ‘Origin of Species’ appeared, published them in an article ‘Versuche über Pflanzen-Hybriden’ (Experiments with plant hybrids).

    No one before him had attempted to use mathematics and statistics as a means of understanding and predicting biological processes and during his lifetime and for some time after, his results were largely ignored.

    Around the time of Mendel’s death, scientists using ever improving optics to study the minute architecture of cells coined the term ‘chromosome’ to describe the long, stringy bodies in the cell nucleus.

    The seven traits studied in peas
    TRAIT DOMINANT TRAIT RECESSIVE TRAIT
    Type of seed surface smooth wrinkled
    Colour of seed albumen yellow green
    Colour of seed coat grey white
    Form of ripe pod inflated constricted
    Colour of unripe pod green yellow
    Position of flowers on stem axial terminal
    Length of stem tall short

    ‘There is doubt as to the probity of this Jesuit scholar, some claiming that his data was falsified whilst others argue that it is accurate’
    Pilgrim, I. (1984) The Too-Good-to-be-True Paradox and Gregor Mendel. Journal of Heredity,#75, pp 501-2. Cited in Brake,M.L. & Hook, N. Different Engines – How science drives fiction and fiction drives science

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    ALBERT MICHELSON (1852-1931) EDWARD MORLEY (1838-1923)

    1887 – USA

    ‘The aim of the experiment was to measure the effect of the Earth’s motion on the speed of light’

    This celebrated experiment found no evidence of there being an effect.

    picture of the Nobel medal - link to nobelprize.org

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    nobelprize_org_colorbox_logo - link to http://www.nobelprize.org/nobel_prizes/physics/laureates/2001/illpres/introduction.html

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    ALEXANDER GRAHAM BELL (1847-1922)

    1875 – USA

    ‘The inventor of the telephone, Bell devoted much of his life to working with the deaf’

    After emigrating to Canada from Scotland in 1870, Bell met Thomas Watson, who would help Bell’s theoretical ideas become physical reality. Bell believed that if the right apparatus could be devised, sound waves from the mouth could be converted into electric current, which could then be sent down a wire relatively simply and converted into sound at the other end using a suitable device. Bell’s telephone was patented in 1876.

    Bell used the money brought in from his invention to found his company AT & T and the Bell Laboratories.

    Just as THOMAS EDISON improved the viability of Bell’s telephone, so Bell enhanced Edison’s phonograph.

    Bell spent some time educating Helen Keller and was instrumental in founding the journal ‘Science‘.

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    THOMAS ALVA EDISON (1847-1931)

    1875 – USA

    ‘We don’t know one millionth of one percent of anything’

    photo portrait of THOMAS ALVA EDISON ©

    THOMAS ALVA EDISON

    ‘Genius is one percent inspiration and ninety-nine percent perspiration’
    Scorning high-minded theoretical and mathematical methods was the basis of Edison’s trial and error approach to scientific enquiry and the root of his genius.

    1877 – Patents the carbon button transmitter, still used in telephones today.
    1877 – Invents the phonograph.
    1879 – Invents the first commercial incandescent light after more than 6000 attempts at finding the right filament and finally settling on carbonized bamboo fibre.

    Edison held 1093 patents either jointly or singularly and was responsible for inventing the Kinetograph and the Kinetoscope (available from 1894) the Dictaphone, the mimeograph, the electronic vote-recording machine and the stock ticker.

    His laboratory was established at Menlo Park in 1876, establishing dedicated research and development centres full of inventors, engineers and scientists. In 1882 he set up a commercial heat, light and power company in Lower Manhattan, which became the company General Electric.

    Experimenting with light bulbs, in 1883 one of his technicians found that in a vacuüm, electrons flow from a heated element – such as an incandescent lamp filament – to a cooler metal plate.
    The electrons can flow only from the hot element to the cool plate, but never the other way. When English physicist JOHN AMBROSE FLEMING heard of this ‘Edison effect’ he used the phenomenon to convert an alternating electric current into a direct current, calling his device a valve. Although the valve has been replaced by diodes, the principle is still used today.

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    WILHELM GOTTLIEB DAIMLER (1834-1900)

    1885 – Germany

    Daimler was convinced that steam power was outdated. In 1885 he perfected the first petroleum-injected internal combustion engine and produced the first motorcycle and the first four-wheeled petrol driven car.

    early motor vehicle

    The foundation for Daimler’s work had already been laid in the creation of two and four-stroke gas-fuelled internal combustion engines by early pioneers Joseph Etienne Lenoir (1822-1900), Alphonse Beau de Rochas (1815-93) and Nikolaus August Otto (1832-91).

    Daimler-Benz

    Although liquid petroleum was well-known, it had been of no use in developing the internal combustion engine because the liquid could not be compressed in the same manner as gas. The four-stroke engine awaited the development of the carburetor, which converted the liquid petroleum into a thin spray, which could be compressed and sparked.

     

    photo portrait of DAIMLER & BENZ ©

    DAIMLER & BENZ

    In 1885 Karl Benz (1844-1929) designed and constructed a three-wheel vehicle powered by a 0.75 horsepower engine.

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    GEORGE FITZGERALD (1851-1901) HENDRICK LORENTZ (1853-1928)

    1890 – Ireland
    1904 – Holland

    ‘A moving object appears to contract’

    The contraction is negligible unless the object’s speed is close to the speed of light.

    In 1890 Fitzgerald suggested that an object moving through space would shrink slightly in its direction of travel by an amount dependent on its speed.

    In 1904 Lorentz independently studied this problem from an atomic point of view and derived a set of equations to explain it. A year later, Einstein derived Lorentz’s equations independently from his special theory of relativity.

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