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Mendel
The field of genetics had been initiated by the work of Gregor Mendel who in 1865 proposed the basic laws of heredity based on the observations from breeding pea plants. -
DNA discovery
Frederick Miescher isolates DNA from cells for the first time and calls it “nuclein”. -
Mitosis
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. -
Chromosome Theory of Inheritance
Walter Sutton observes that the segregation of chromosomes during meiosis matched the segregation pattern of Mendel’s -
First use of the word GENE
Wilhelm Johannsen coins the word “gene” to describe theMendelian unit of heredity. He also uses the terms genotypeand phenotype to differentiate between the genetic traits of anindividual and its outward appearance. -
Existance of Sex Chromosomes
Thomas Morgan’s experiments in 1910 with the fruit fly (Drosophila) revealed the existence of the sex chromosomes and confirmed that genes reside on chromosomes. -
DNA as Hereditary Material
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. -
Complementary Basys
Edwin Chargaff discovered that adenine and thymine exist in equal proportions in all organisms, as do cytosine and guanine, but that the proportions between the two pairs differ depending on the organism. -
Confirming DNA as vessel for Inheritance
The Hershey–Chase experiments were a series of experiments conducted in 1952 by Alfred Hershey and Martha Chase that helped to confirm that DNA was the genetic material. 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. -
Discovery of the Double Helix
Franklin is best known for her work on the X-ray diffraction images of DNA which led to discovery of DNA double helix. Her data, according to Francis Crick, was "the data we actually used to formulate Crick and Watson's 1953 hypothesis regarding the structure of DNA. Franklin's X-ray diffraction images confirming the helical structure of DNA were shown to Watson without her approval or knowledge. -
Double Helix
James D. Watson and Francis Crick were the two co-discoverers of the structure of DNA in 1953. They used x-ray diffraction data collected by Rosalind Franklin and proposed the double helix or spiral staircase structure of the DNA molecule. -
Humans have 46 Chromosomes
Joe Hin Tjio finds that Human genome consists of 46 Chromosomes. -
DNA polymerase
Arthur Kornberg and colleagues isolated DNA polymerase, an enzyme that would later be used for DNA sequencing. -
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. -
mRNA
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. -
Restriction Enzymes
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 mappinggenomes. -
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
Sanger began using the enzyme DNA polymerase to make new strands of DNA from single-strand templates, introducing radioactive nucleotides into the new DNA. It generated a series of DNA molecules of varying lengths that could be separated by using polyacrylamide gel electrophoresis, and then the DNA sequence could be determined. -
Introns
Richard Roberts’ and Phil Sharp’s labs show that eukaryotic genes contain many interruptions called introns. These non-coding 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. -
PCR
Kary Banks Mullis developed Polymerase Chain Reaction or PCR. The polymerase chain reaction (PCR) is a scientific technique in molecular biology to amplify a single or a few copies of a piece of DNA across several orders of magnitude, generating thousands to millions of copies of a particular DNA sequence. -
Gene Replacement
First gene replacement therapy-T cells of a four-year old girl were exposed outside of her body to retroviruses containing an RNA copy of a normal ADA gene. This allowed her immune system to begin functioning. -
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. -
FIrst Clone
Dolly (5 July 1996 – 14 February 2003) was a female domestic sheep, and the first mammal to be cloned from an adult somatic cell, using the process of nuclear transfer.[1][2] She was cloned by Ian Wilmut, Keith Campbell and colleagues at the Roslin Institute and the biotechnology company PPL Therapeutics near Edinburgh in Scotland. -
Drosophila Genome
The Drosophila genome is completed. The Arabidopsis genome is completed. The human genome is reported to be completed. -
Human Genome Project
The Human Genome Project is officially completed after being funded by Congress in 1988. Within the limits of today's technology, the human genome is as complete as it can be. Small gaps that are unrecoverable in any current sequencing method remain, accounting for about 1 percent of the gene-containing portion of the genome, or euchromatin. New technologies will have to be invented to obtain the sequence of these regions
