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Charles Darwin introduces "On the Origin of Species"
Charles Darwin published in 1859 "On the Origin of Species by Means of Natural Selection or The Preservation of Favored Races in the Struggle for Life". His key premise was that evolution occured through the selection of iinheritance and transmission rather than acquired characteristics between individual members of a species. -
Gregor Mendel's Famous Discovery
Mendel cross-pollinated yellow and green pea seeds exclusively. Mendel found that the first generation always had yellow peas. However, the following generation consistently had a 3:1 ratio of yellow to green peas. He came to three important conclusions: the inheritance of each trait are passed on to descendents unchanged, an individual inherits one such unit from each parent for each trait, and a trait may not show up in an individual but can still be passed on to the next generation. -
Johannes Friedrich Miesche
Johannes Friedrich Miesche was a Swiss physician and biologist. He isolated various phosphate-rich chemicals, which he called nuclein from the nuclei of white blood cells. This paved the way for the identification of DNA as the carrier of inheritance. -
William Bateson and Reginald Crundall Punnett
William Bateson and Reginal Crudell Punnett demonstrated actions of some genes and modified actions of other genes. This is the first time gene regulation was demonstrated -
Reginald Crundall Punnett
Punnett developed the Punnett Square. It is used to depict the number and variety of genetic combinations. -
Thomas Hunt Morgan
Thomas Hunt Morgan did experiments with fruit flies. He proved that the genes responsible for the appearance of a specific phenotype were located in the chromosomes. He also found that genes on the same chromosome do not always assort independently. -
Rosalind Franklin and Maurice Wilkins
Rosalind Franklin and Maurice Wilkins performed X-ray crystallography studies of DNA. This provided crucial information that led to the elucidation of the structure of DNA. -
James Watson and Francis Crick Propose a Double Helix Model for DNA
Rosalind Franklin, a British chemist, used the X-ray diffraction technique to capture the first high-quality images of the DNA molecule. Franklin’s colleague Maurice Wilkins showed the pictures to James Watson who had been working with Francis Crick, a British biophysicist, on the structure of the DNA molecule. These pictures gave Watson and Crick enough information to propose the double-stranded model for DNA. -
Marshall Nirenberg, Heinrich Matthaei, and Severo Ochoa crack The Genetic Code
Marshall Nirenberg, Heinrich Mathaei and Severo Ochoa demonstrated that a sequence of three nucleotide bases determines each of the 20 amino acids. This means that there are 64 possible combinations for 20 amino acids. They formed synthetic mRNA by mixing the nucleotides of RNA with a special enzyme called polynucleotide phosphorylase. This resulted in the formation of a single-stranded RNA. -
The cloned sheep "Dolly" is presented
On July 5, 1996 a sheep was born as a clone of the cell of another sheep. This sheep, called Dolly, was the first mammal to be cloned from an adult cell. -
Paul Berg
Paul Berg created the first recombinant DNA molecules by combining the DNA of two different organisms. Berg used a restriction enzyme to isolate a gene from a human-cancer-causing virus. Then, he used ligase to join the section of virus DNA with a molecule of DNA from the bacterial virus lambda, creating the first recombinant DNA molecule. -
Frederick Sanger
Frederick Sanger was first credited with the invention of DNA sequencing. During experiments, he developed the basics of modern sequencing methods. Sanger's approach involved copying DNA strands which would show the location of the nucleotides in the strands. Then he had to analyse the composite collections of DNA pieces detected from the four test tubes, one for each of the nucleotides found in DNA. Then they needed to be arranged in the correct order. -
Kary Mullis
Kary Mullis at Cetus Corporation invented polymerase chain reaction (PCR). PCR is a method for multiplying DNA sequences in vitro. The purpose of the Polymerase Chain Reaction is to make a huge number of copies of a specific DNA fragment, a gene for instance. PCR can be used for instance sequencing. -
Human Genome Project Launched
The U.S. Human Genome Project started as a 15-year effort co-ordinated by the U.S. Department of Energy and the National Institutes of Health.
Project goals were to identify all the genes in human DNA, determine the sequences of the 3 billion chemical base pairs that make up human DNA, store this information in databases, improve tools for data analysis, transfer related technologies to the private sector, and address the ethical, legal, and social issues (ELSI) that may arise from the project. -
Barbara McClintock
Barbara McClintock discovers that genes can move on a chromosome and jump from one chromosome to another. She studied the inheritance of color and pigment distribution in corn kernels. Scientists now think transposons may be linked to some genetic disorders such as hemophilia, leukemia, and breast cancer. They also think that transposons have played a crucial role in evolution.
