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Natural Selection
Charles Darwin wrote “On the Origin of Species by Means of Natural Selection, or the Preservation of Favored Races in the Struggle for Life. -
Heredity Transmitted in Units
Gregor Mendel’s experiments on peas demonstrate that heredity is transmitted in discrete units. -
DNA Isolated
Rederick Miescher isolates DNA from cells for the first time and calls it “nuclein”. -
Discovery: Mitosis
Described Walter Flemming describes chromosome behavior during animal cell division. He stains chromosomes to observe them clearly and describes the whole process of mitosis in 1882. -
Rediscovery of Mendel’s work
Botanists DeVries, Correns, and von Tschermak independently
rediscover Mendel’s work while doing their own work on the
laws of inheritance. The increased understanding of cells and
chromosomes at this time allowed the placement of Mendel’s
abstract ideas into a physical context. -
Chromosome Theory of Inheritance
Walter Sutton observes that the segregation of chromosomes
during meiosis matched the segregation pattern of Mendel’s -
Orderly Inheritance of Disease 1902
A British physician, Archibald Garrod, observes that the
disease alkaptonuria is inherited according to Mendelian rules.
This disease involves a recessive mutation, and was among the
first conditions ascribed to a genetic cause. -
The Word Gene is Coined
Wilhelm Johannsen coins the word “gene” to describe the
Mendelian unit of heredity. He also uses the terms genotype
and phenotype to differentiate between the genetic traits of an
individual and its outward appearance. -
Chromosomes Carry Genes
Thomas Hunt Morgan and his students study fruit fly
chromosomes. They show that chromosomes carry genes, and
also discover genetic linkage. -
One Gene, One Enzyme Hypothesis
George Beadle and Edward Tatum’s experiments on the red
bread mold, Neurospora crassa, show that genes act by
regulating distinct chemical events. They propose that each
gene directs the formation of one enzyme -
DNA Has a Regular Periodic Structure
William Astbury, a British scientist, obtains the first X-ray
diffraction pattern of DNA, which reveals that DNA must
have a regular periodic structure. He suggests that nucleotide
bases are stacked on top of each other. -
DNA Transforms Cells
Oswald Avery, Colin MacLeod, and Maclyn McCarty show
that DNA (not proteins) can transform the properties of cells --
thus clarifying the chemical nature of genes. -
Jumping Genes
Barbara McClintock, using corn as the model organism,
discovers that genes can move around on chromosomes. This
shows that the genome is more dynamic than previously
thought. These mobile gene units are called transposons and
are found in many species. -
Genes Are Made of DNA
Alfred Hershey & Martha Chase show that only the DNA of a
virus needs to enter a bacterium to infect it, providing strong
support for the idea that genes are made of DNA -
DNA Double Helix
Francis H. Crick and James D. Watson described the double
helix structure of DNA. They receive the Nobel Prize for their
work in 1962. -
46 Human Chromosomes
Joe Hin Tjio defines 46 as the exact number of chromosomes in
human cells. -
DNA copying enzyme
Arthur Kornberg and colleagues isolated DNA polymerase, an
enzyme that would later be used for DNA sequencing. -
Cause of Disease Traced to Alteration
Vernon Ingram discovers that a specific chemical alteration in
a hemoglobin protein is the cause of sickle cell disease. -
Semiconservative Replication of DNA
Matthew Meselson and Franklin Stahl demonstrate that DNA
replicates semiconservatively: each strand from the parent
DNA molecule ends up paired with a new strand from the
daughter generation. -
Chromosome Abnormalities Identified
Jerome Lejeune and his colleagues discover that Down
Syndrome is caused by trisomy 21. There are three copies,
rather than two, of chromosome 21, and this extra
chromosomal material interferes with normal development. -
First Screen for Metabolic Defect in Newborns
Robert Guthrie develops a method to test newborns for the
metabolic defect, phenylketonuria (PKU). -
mRNA Ferries Information
Sydney Brenner, François Jacob and Matthew Meselson
discover that mRNA takes information from DNA in the
nucleus to the protein-making machinery in the cytoplasm. -
Genetic Code Cracked
Marshall Nirenberg and others figure out the genetic code
that allows nucleic acids with their 4 letter alphabet to
determine the order of 20 kinds of amino acids in proteins. -
First Restriction Enzyme Described
Scientists describe restriction nucleases, enzymes that
recognize and cut specific short sequences of DNA. The
resulting fragments can be used to analyze DNA, and these
enzymes later became an important tool for mapping
genomes. -
First recombinant DNA
Scientists produce recombinant DNA molecules by joining
DNA from different species and subsequently inserting the
hybrid DNA into a host cell, often a bacterium. -
First animal gene cloned
Researchers fuse a segment of DNA containing a gene from
the African clawed frog Xenopus with DNA from the
bacterium E. coli and placed the resulting DNA back into an
E. coli cell. There, the frog DNA was copied and the gene it
contained directed the production of a specific frog protein. -
DNA Sequencing
Two groups, Frederick Sanger and colleagues, and Alan
Maxam and Walter Gilbert, both develop rapid DNA
sequencing methods. The Sanger method is most commonly
employed in the lab today, with colored dyes used to identify
each of the four nucleic acids that make up DNA -
First Genetic Engineering Company
Herbert Boyer founds Genentech. The company produces the
first human proteinin a bacterium, and by 1982 markets the
first recombinant DNA drug, human insulin. -
Introns Discovered
Richard Roberts’ and Phil Sharp’s labs show that eukaryotic
genes contain many interruptions called introns. These noncoding
regions do not directly specify the amino acids that
make protein products. -
First Transgenic Mice and Fruit Flies
Scientists successfully add stably inherited genes to laboratory
animals. The resulting transgenic animals provide a new way
to test the functions of genes. -
GenBank Database Formed
Scientists begin submitting DNA sequence data to a National
Institutes of Health (NIH) database that is open to the public. -
First Disease Gene Mapped
A genetic marker for Huntington’s disease is found on
chromosome 4. -
PCR Invented
The polymerase chain reaction, or PCR, is used to amplify
DNA. This method allows researchers to quickly make billions
of copies of a specific segment of DNA, enabling them to study
it more easily. -
First Time a Disease Gene is Positionally Cloned
A method for finding a gene without the knowledge of the
protein it encodes is developed. So called, positional cloning
can help in understanding inherited disease, such as muscular
dystrophy. -
First Human Genetic Map
The first comprehensive genetic map is based on variations in
DNA sequence that can be observed by digesting DNA with
restriction enzymes. Such a map can be used to help locate
genes responsible for diseases. -
Yeast Artificial Chromosomes
Scientists discover that artificial chromosomes made from
yeast can reliably carry large fragments of human DNA
containing millions of base-pair pieces. Earlier methods used
plasmids and viruses, which can carry only a few thousand
base-pair pieces. The ability to deal with much larger pieces
of DNA makes mapping the human genome easier. -
Microsatellites Are New Genetic Markers
Repetitive DNA sequences called microsatellites are used as
genetic landmarks to distinguish between people. Another type
of marker, sequence–tagged sites, are unique stretches of DNA
that can be used to make physical maps of human
chromosomes. -
Launch of the Human Genome Project
The Department of Energy and the National Institutes of
Health announce a plan for a 15-year project to sequence the
human genome. This will eventually result in sequencing all 3.2
billion letters of the human genome. -
ESTs, Fragments of Genes
An expressed-sequence tag (EST) an identified piece of a gene,
is made by copying a portion of a messenger RNA (mRNA)
molecule. As such, ESTs provide a way to focus on the
“expressed” portion of the genome, which is less than one-tenth -
Second-Generation Genetic Map of Human Genome
A French team builds a low-resolution, microsatellite genetic
map of the entire human genome. Each generation of the map
helps genetics. -
FLAVR SAVR Tomato
The Food And Drug Administration approves the sale of the
first genetically modified food. -
Ban on Genetic Discrimination in the Workplace
Protection under the American with Disabilities Act is
extended to cover discrimination based on genetic
information. -
Mouse Genetic Map Completed
The lab mouse is valuable for genetics research because
humans and mice share almost all of their genes, and the
genes on average are 85% identical. The mouse genetic
increases the utility of mice as animal models for genetic
disease in humans. -
E. coli Genome Sequenced
The complete sequence of the E. coli genome will help
scientists learn even more about this extensively studied
bacterium -
M. tuberculosis Bacterium Sequenced
Mycobacterium tuberculosis causes the chronic infectious
disease tuberculosis. The sequencing of this bacterium is
expected to help scientists develop new therapies to treat the
disease. -
Roundworm C. elegans Sequenced
The first genome sequence of a multicellular organism, the
round worm, Caenorhabditis elegans, is completed. -
Chromosome 22 Sequenced
The first finished, full-length sequence of a human chromosome
is produced. Chromosome 22 was chosen to be first because it is
relatively small and had a highly detailed map already
available. Such a map is necessary for the clone by clone
sequencing approach. -
Human Genome Working Draft Completed
By the end of Spring 2000, HGP researchers sequence 90
percent of the human genome with 4-fold redundancy. This
working draft sequence is estimated to be 99.9% accurate -
Mouse Genome Working Draft Assembled and Analyzed
The Mouse Genome Sequencing Consortium publishes an
assembled draft and comparative analysis of the mouse
genome. This milestone was originally planned for 2003. -
Rat Genome Working Draft Completed
By Fall 2002, researchers sequence over 90% of the rat genome
with over 5-fold redundancy. -
Completion of the Human Genome Sequencing
The finished human genome sequence will be at least 99.99%
accurate. -
Identical twins have differences in their genetic
DNA Worldwide and Eurofins Forensic discover identical twins have differences in their genetic makeup In 2013, DNA Worldwide and their laboratory partners Eurofins Forensic were the first in the world to prove that twins have differences in their genetic makeup. -
Creation of an organism with an expanded artificial genetic code
Further Breakthroughs Throughout 2014 the world’s scientists have continued to develop their understanding of DNA. Researchers announced in May that they had successfully created an organism with an expanded artificial genetic code. This success could eventually lead to the creation of organisms that can produce medicines or industrial products organically.
