History of Cell Biology

During the 17th Century

· 1665 Robert Hooke had successfully invented the microscope. Because of this discovery, Robert Hooke was the first one to have a close look of a cell appears to be. His description of these cells was published in Micrographia. However, the cell walls observed by Hooke gave no indication of the nucleus and other organelles found in most living cells.

· 1674  A live cell was observed by Anton van Leeuwenhoek, the very first successful effort to do such.

 
During the 18th Century

· There were not much discovery in the field of Cell Biology during this time. It took another hundred years after those first cell observations for the ubiquitous nature of cells to be fully recognized.

During the 19th Century

·1825 French scientist Francoise Raspail established one of the concepts of cell theory: that all cells arise from pre-existing cells. The basis of this was the witnessing of binary fission under a microscope wherein a single cell divided into two daughter cells.

·1836 Theodore Schwann and Matthias Scleiden proposed the cell theory in 1836. The concept of the theory holds that: (1) The cell is the unit of structure, physiology, and organization in living things, (2) The cell retains a dual existence as a distinct entity and a building block in the construction of organisms, (3) Cells form by free-cell formation, similar to the formation of crystals (spontaneous generation).

·1855 The third doctrine of Schwann and Scleiden was proven wrong by Rudolf Virchow. In this year, he formally enunciated in his powerful dictum that, “Omnis cellula e cellula“, which is translated as “All cells only arise from pre-existing cells“.

· In the middle of the 19th century, Scientists had accepted the fact that it was simply not possible to view cell structures which measure less than a half of a micrometer with the use of a microscope. But because of the development of the cathode ray tube, they’ve later discovered that aside from using light, electrons can be used to view these structures.

20th Century up to the present

·        1919 Phoebus Levene, a Russian physician and chemist, first discovered the order of the three major components of a single nucleotide (phosphate, pentose sugar, and nitrogenous base). He was also the first to discover the carbohydrate component of RNA (ribose), and carbohydrate component of DNA (deoxyribose). Years later, Levene finally identified how DNA and RNA molecules are put together

·1933 The first prototype of the electron microscope was constructed. It is a type of microscope which utilizes a beam of electrons to create an image of the specimen.

·1943 A scientist named Erwin Chargaff began to challenge Levene’s previous conclusions. In 1950, he noted that the nucleotide composition of DNAdiffers among species and do not repeat in the same order reached two major conclusions.

· Chargaff concluded that almost all DNA, no matter what organism or tissue type it comes from, still maintains certain properties, even as its composition varies. He postulated the “Chargaff’s Rule” which says that the amount of cytosine is equal to the amount of guanine, and the amount of thymine is equal to the amount of adenine. In short, the total amount of pyrimidines (thymine and cytosine) approximates the amount of purines (adenine and guanine).

·1951 Meanwhile in the field of cytology, George Grey has successfully made the first continuous cell line to be cultured. The cell line was derived from the cervical cancer cells of Henrietta Lacks, thus these cells were referred to as HeLa cells. These cells played a significant role in the course of cell biology.

·1953 James Watson and Francis Crick derived the three-dimensional and double helical model of the DNA (Pray 2009). After that, the process of replicating the DNA was discovered.

·1961 The endeavor of cracking the genetic code started.
As with the rapid growth of molecular biology in the mid-20th century, cell biology research exploded. It became possible to maintain, grow, and manipulate cells outside of living organisms. The minimal media requirements for cells were characterized years later. Sterile cell culture techniques were further developed.

·  Further advances in electron microscopy greatly facilitated the development of transfection methods. The process of genetic engineering, or the act of modifying an organism’s genetic material either by adding genes or deleting some parts of it, was declared as a separate field in the 1970s.

·1970 Reverse transcriptase in retroviruses was first discovered.

·1977 Frederick Sanger introduced the process of DNA sequencing. The first ever organism to have its genome sequence is a bacteriophage.

·1980 The Polymerase Chain Reaction, a method used to amplify a copy of a segment of a DNA was inverted by Kary Mullis .

1998 Hamilton and Baulcombe discovered the siRNA as part of post-transcriptional gene silencing in plants.