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500
Aristotle and Plato
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Period: 500 to Apr 25, 1300
First theorists of genetics
A.D. 500-1300
The ancient Greek philosopher Aristotle, thought that the male semen contributed the "active element" to the offspring, bringing it to life, while the female contributed only nutritional material for the offspring. (See Aristotle) -
The microscope is invented by Janssen.
Dutch spectacle-makers Hans Janssen and his son Zacharias Janssen invented the first microscope in 1590. As further progression naturally occured scientists have made major contributions due to this invention. (See Janssen) -
The Term Cell: Robert Hooke
Robert Hooke, an English physicist looked through a microscope lens at a piece of cork. He recorded his observations and became the first to observe and use the term “cell”. His recordings are extremely significant to the field of Microscopy. He believed at the time that these cells only lived in plants and therefore would only observe plant materials. His first book entitled Micrographia, and wrote Hooke’s law. (See Hooke's Law) -
Leeuwenhoek discovers bacteria
Known for his open mind and large curiosity, Antony van Leeuwenhoek had no formal education, and was only fluent in his native Dutch. He invented over 500 microscopes while working as a draper. He began to observe many varieties of matter under his microscope that magnified over 200 times. He hired a artist to illustrate his descriptions. He then wrote to the Royal Society of London and stayed in contact with them for the next fifty years. (See Leeuwenhoek, bacteria) -
Discovery of the Nucleus
Discovery of the nucleus: Robert Brown was the first to use the term “nucleus” in a paper to the Linnaean Society and it was published in 1833, he sensed that this observation of an opaque spot on plant cells was important and documented it accordingly. (see nucleus) -
Mendel's Study of Peas
Mendel, in his study of peas, discovers that traits are transmitted from parents to progeny by discrete, independent units, later called genes. His observations laid the groundwork for the field of genetics. And all experiments were performed without any prior knowledge of meiosis. He published in 1865. (See Mendel, meiosis) -
First Vaccine
Jenner inoculates a child with a viral vaccine to protect him from smallpox. This was the first vaccine ever developed. An English country doctor named Edward Jenner inoculated James Phillips, and eight year old boy, with the cow pox virus. He based this experiment on the observation that milk maidens would not exhibit signs of cow pox. This was caused by the similarities to developing another disease from working with cows and the separate virus would protect them. (See Jenner, inoculation) -
Edouard van Benden
Edouard van Benden, while observing roundworms discovered that the sperm and egg cells had two chromosomes while fertilized eggs had four. He concluded that the number of chromosomes in any body cell is constant, as well as a species is identifiable by the number of chromosomes it contains. For example humans are identified by our 23 chromosome pairs. Also through his observations of sex cells he concluded that gametes only have half the usual chromosome count. -
Walhter Flemming, the formation of mitosis
Walhter Flemming described the separation of threads within the nucleus: mitosis. He also formulated the names mitosis and chromatin. He was extremely articulate with documenting information. Flemming observed that the red dye was heavily absorbed by granular-appearing structures in the nucleus, and named these structures chromatin, from the Greek word for color. (See Flemming) -
August Weismann presented the theory that a special division takes place in sex cells.
He began to explain reduction division (today known as meiosis). He alongside with van Benden helped the understanding of Mendel’s theories. This was just prior to the rediscovery of Mendel’s experiments in 1900. He theorized that in multicellular organisms there were two types of cells, germ cells and somatic cells. Germ cells, such as sperm carry biological information and somatic cells as the offspring of germ cells. (See Weismann, somatic cell) -
Rediscovery of Mendel's Experiments
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Sutton's Chromosomal theory of Inheritance
Chromosomal Theory was also established in 1902 by Sutton individually
The development and refinement of the microscope opened the insight for major transitions of study: cell biology and genetics.
The chromosomal theory of inheritance:
1) Chromosomes carry genes
2) Paired chromosomes separate during meiosis. Both sex cells are observed with half the number of chromosomes which are observed in somatic cells. Each gamete only has one of each paired allele.
(See Sutton) -
Development of the Chromosomal Theory
American and German scientist, Walter S. Sutton and Theodor Boveri, discovered that chromosomes are pairs which separate during meiosis. These segregated pieces later match up when egg and sperm bond.
(See Sutton, Boveri) -
Sutton and Boveri
American and German scientist, Walter S. Sutton and Theodor Boveri, discovered that chromosomes are pairs which separate during meiosis. These segregated pieces later match up when egg and sperm bond. -
Morgan establishes the chromosomal theory of heredity
Thomas Hunt Morgan (1866-1945) establishes the chromosomal theory of heredity.
Morgan confirmed Mendelian laws of inheritance and the hypothesis that genes are located on chromosomes, he also discovered that eye color in Drosophila expressed a sex-linked trait. (See sex linked trait) -
Vaccine Efforts for fighting pneumonia
Frederick Griffiths attempted to create a vaccine against strephoccous pneumonia, a bacteria causing pneumonia. (For results see Evidence of Hereditary Material) -
Avery reported significant findings based on Griffith's experiments
Avery and colleagues reported findings from Griffith’s unusual results. Including that the hereditary material in the extracts was DNA and was not the proteins found in the chromosome. (See Avery) -
Barr Body
Dr. Murray Barr at the university of Western Ontario discovered that the nuclei of nerve cells in female cats contained a dense mass of chromatin (sex chromatin body), which lacked in male cells. This sex chromatin body was named a Barr Body. (See Barr, Barr Body, sex chromatin) -
The Contributions of Rosalind Franklin
Rosalind, alongside with Maurice Wilkins used X- ray diffraction to help determine the structure of the DNA molecule. She also discovered the sugar- phosphate backbone of the molecule, the helical structure consisting of double strands, and assumed quantitative details about the shape and size before Watson and Crick. (See Franklin, Wilkins, X- ray diffraction) -
Watson and Crick, the formulation of the helical structure of DNA
Watson and Crick presented the public with their three dimensional model of DNA. This structure with very few modifications is still used today, a double helix shape with sugar and phosphate molecules forming a backbone while nitrogenous bases form the rungs. Two nitrogenous bases are pair together by a hydrogen bond. It is composed of several molecules of sugars, phosphates and nitrogenous bases. (See Watson, Crick, DNA molecule) -
DNA sequencing
Walter Gilbert and Frederick Sanger, an American and English scientist, working separately developed new techniques for rapid DNA sequencing. Both methods, although implying different techniques (Gilbert was multiplying, dividing, and carefully fragmenting DNA, while Sanger revealed the precise nucleotide sequence of DNA, by working with the positions of the bases) now make it possible to read nucleotide sequence for entire genes, which are known to range from 1,000- 30,000 bases long. -
Sophie makes AWESOME influential timeline, significant to all future Biology discoveries