2. • Cells can be observed with microscope
• The discovery of cells is generally credited to
Robert hooke
• He was an English microscopist who at age of 27,
awarded the position of curator of Royal Society
of London.
• In 1665, he took a good clear piece of cork and
then examined it with a microscope.
• Hooke called the pores as cells.
• He observed the empty cell walls of dead plant
tissue.
3. • Anton van Leeuwenhoak, a dutchman who used
to grind lenses and thus constructed simple
microscope.
• He was first to examine a drop of pond water
under microscope and observe the teeming
microscopic particles named “animacules”.
• He was also first to describe various forms of
bacteria, which he obtained from water and from
scrapings of his teeth.
• He wrote some letters to the Royal society
describing this previously unseen world, where
Robert Hooke confirm the observations.
4. • In 1838, Matthias Schleiden, a German botanist
concluded that plants were made of cells and
that the plant embryo arose from single cell.
• In 1839, Theodore Schwann, a German zoologist
published a comprehensive report on cellular
basis of animal life.
• He concluded that the cells of plants and animals
are similar structure and proposed the cell
theory:
• All organisms are composed of one or more cells.
• The cell is the structural unit of life.
5. • In 1855, Rudolf Virchow, a German pathologist, made a
convincing case for the third tenet of the cell theory and
stated that calls can only arise by division from a pre-
existing cell.
• In 1857, Albert von Kölliker described what he called
“granules" in the cells of muscles. Richard Altmann in 1890,
established them as cell organelles and called them
"bioblasts". The term "mitochondria" was coined by Carl
Benda in 1898.
• Flemming was the first to detail the chromosomal
movements in the process of mitosis. In 1879, Flemming
used aniline dyes, a by-product of coal tar, to stain cells of
salamander embryos. He was able to visualize the
threadlike material as the cells divide. He saw that
chromosomes were "doubled" when they appeared in
prophase, and "solved" the problem of chromosomal
partitioning between mother and daughter cells.
6. • In 1885 Weismann had published "The Continuity
of the Germ-Plasm as the Foundation of a Theory
of Heredity“. He stated that only the hereditary
substance of the germ cells was inheritable, and
that cells that derive from all other parts of
parents' bodies (soma cells), could not transmit
from parents to offsprings.
• The existence of the cell organelle which is now
known as Golgi apparatus or Golgi complex, or
simply as 'the Golgi", was first reported by
Camillo Golgi in 1898, when he described in
nerve cells an 'internal reticular apparatus'
impregnated by a variant of his chromoargentic
staining.
7. • In 1951 George and Martha Grey of Johns
Hopkins University, successfully made the first
continuous cell line culture of Human cells.
The cell line was derived from the cervical
cancer cells of Henrietta Lacks, thus these cells
were referred to as HeLa cells.
• Hela cells- descended by cell division from this
first cell sample are still being grown in
laboratories around the world today.
8. • In 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).
• In 1950 , scientist named Erwin Chargaff noted
the nucleotide composition of DNA molecule among
species and 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 1953 James Watson and Francis Crick derived the three-
dimensional and double helical model of the DNA.
•
9. • 1956 George Emil Palade showed the site of enzymes
manufacturing in the cytoplasm is made on ribosomes.
• 1957 – Meselson, Stahl and Vinograd developed density
gradient centrifugation in cesium chloride solutions for
separating nucleic acids.
• 1958 The Meselson-Stahl demonstrate that DNA is
semiconservatively replicated.
• In 1970, Smith and Kent W. Wilcox discovered the first type II
restriction enzyme , HindII.
• 1970 Reverse transcriptase in retroviruses was first
discovered.
• 1972 Paul Berg used a restriction enzyme to cut DNA and
ligase to join two DNA strands together to form hybrid circular
molecule.
10. • 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.
• 1986, the term “Genomics” appeared for the first time to
describe the scientific discipline of mapping and analysing
genes.
• 1986 Leroy Hood: Developed automated sequencing
mechanism.
• 1986 Human Genome Initiative was announced.
• 1995 Moderate-resolution maps of chromosomes 3, 11, 12,
and 22 were published.
• These maps provide the locations of “markers” on each
chromosome to make locating genes easier.
11. • 1995 John Craig Venter: First bacterial
genomes sequenced.
• 1995 Automated fluorescent sequencing
instruments and robotic operations .
• 1996 First eukaryotic genome-yeast-
sequenced.
• 1999 First Human chromosomes (number22)
sequenced.
• April 2003 Human Genome Project was
Completed.
