Louis Pasteur- He was a French chemist and biologist best known for his discoveries in microbiology. His experiments confirmed the germ theory of disease and he discover that microbes, viruses and bacteria makes the diseases, also reducing mortality from puerperal fever, and he created the first vaccine against rabies. He is best known to the general public for showing how to stop milk and wine from going sour - this process came to be called pasteurization. He is regarded as one of the three main founders of microbiology, together with Ferdinand Cohn and Robert Koch.

Johan Gregor Mendel- He was an Austrian monk, published a paper on genetics that earned him the nickname “the Father of Modern Genetics.” One of Mendel’s jobs at the monastery was to care for the garden. He noticed the differences between the plants of the same kind. From this he developed a theory of genetics that refuted the pangene idea and enabled people to predict the outcome of a genetic cross if the genes of the parents were known. When Mendel first published his paper, the idea of the pangenes it was ignored his work or dismissed it as false. It wasn’t until 1900 that a couple of botanists working on other research rediscovered his work.

In 1870 the process of mitosis, regular cell division by which one cell divides to make two cells, was observed, and researchers noticed that chromosomes, whose function was not understood, were moving around in the cell during mitosis so that each daughter cell got an exact set of them.

James Watson, an American, and Francis Crick, an Englishman, used the x-ray data collected by another scientists to propose a hypothetical structure for DNA molecule, which also showed how DNA could be the genetic code material and suggested a means what it could replicate itself. Another chemical analyses of DNA have confirm their prediction. For their work they received the Nobel Prize award in 1962.


Timeline

1655 - Robert Hooke (1635-1703) of Britain designed his own microscope and discovered matter made up of what he called cells.
1759 - C.F. Wolff (1733-1794) of Germany proposed a general cell theory.
1838 - Matthias J. Schleiden (1804-1881) of Germany published a cell theory as applied to plants.
1839 - Theodor Schwann (1810-1882) of Germany published cell theory as applied to animals.
1857 - Gregor Johann Mendel (1822-1884), an Austrian monk, began experiments with pea plants. He later became known as the "father of genetics."
1859 - English biologist Charles Darwin (1809-1882) published “On the Origin of Species,” explaining units of heredity and variations in species.
1865 - Mendel announced his theories of heredity, known as Mendel’s Laws.
1869 - Sir Francis Galton (1822-1911) of Britain published his book, Hereditary Genius, claiming that heredity alone is responsible for a person’s character traits.
1882 - German biologist Walther Fleming (1843-1905) used dyes to stain cells; he discovered rods he called “chromosomes.”
1886 - Dutch botanist Hugo de Vries (1848-1935) created term “mutation” while experimenting with primroses.
1887 - Belgian biologist Edouard van Beneden (1846-1910) discovered that all organisms of the same species have the same number
1892 - August Weismann (1834-1914) published an essay on heredity. He proposed heredity was transmitted by a substance with a “chemical and molecular constitution”--he greatly influenced subsequent biologists.of chromosomes
1900 - De Vries published a paper that included the laws of inheritance as do two others: German botanist Karl Erich Correns (1864-1933) and Austrian botanist Erich Tschermak von Seysenegg (1871-1962).
1901 - De Vries published a paper on mutations.
1902 - American biologist Walter Stanborough Sutton (1877-1916) demonstrated that chromosomes exist in pairs that are structurally similar.
1903 - Sutton proved that sperm and egg cells have one of each pair of chromosomes
1908 - American biologist Thomas Hunt Morgan (1866-1945) with Alfred H. Sturtevant of the U.S. showed that genes were located on chromosomes; he experimented with Drosophelia (fruit flies) to investigate sex chromosomes, and discovered X and Y chromosomes, sex-linked traits, and crossing-over.
1909 - Danish botanist Wilhelm Ludvig Johannsen (1857-1927) proposed that each portion of a chromosome that controls a phenotype be called a “gene” (Greek: “to give birth to”).
1913 - Alfred Henry Sturtevant (1891-1970) began constructing a chromosome map for Drosophelia (it was completed in 1951 for all four Drosophelia chromosomes).
1919 - Hermann Joseph Muller (1890-1976) of the U.S. experimented with Drosophelia to create more mutant flies
1941 - George W. Beadle (1903-1989) of the U.S. and Edward L. Tatum (1909-1975) of the U.S. discovered that genes control the production of enzymes.
1944 - Oswald T. Avery (1877-1955) of the U.S. announced that DNA alone is the substance responsible for heredity.
1952 - Francis H. C. Crick (1916- ) of Britain and James D. Watson (1928- ) of the U.S. made a model of the DNA molecule and proved that genes determine heredity.