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400 BCE
Galen of Pergamon describes the human body
He performed studies that influenced medicine in the long run. He's known for his discovery of blood in human arteries and for his dissection of the human cranial nerves (nerves that supply key areas of the head, face, and upper chest). -
1546
The Germ Theory of Disease is published
Theory that states that tiny organisms called microbes can invade other organisms and cause disease that are easily passed among humans. -
Lamarck develops Hypothesis of evolution by means of acquired characteristics
His theory stated that an animal gained an extra trait that helped it with life during their lifetime. Ex: Giraffe's long necks. He believed that acquired traits could be passed to offspring. Later on, his hypothesis was eventually proven wrong. -
The Voyage of the HMS Beagle
He went to a few different places and collected samples while recording discoveries at the places. At first, he thought all of his findings weren't really worth anything, but then when he came back and realized the potential. There were differentiations because of evolution between the animals. He contributed to the theory of natural selection by publishing this book. -
The Origin of species by means of Natural Selection is published
Darwin proposed a mechanism (natural selection) for how evolution takes place. Evolution is the process by which living things become adapted to their environment and new species develop. The idea of evolution was already discussed before Darwin but there was no accepted mechanism. Darwin's idea of natural selection filled this gap. -
Louis Pasteur refutes spontaneous generation
Pasteur's broth cultures only got cloudy with microorganisms when the cultures were open. When he sterilized the broth cultures and plugged the openings with cotton, air was still able to get in, but the broth stayed clear. No microbes arose when none could get in. Therefore, microbes were not arising by spontaneous generation. -
Gregor Mendel publishes works on inheritance of traits in pea plants
Mendel use to selectively breed pea plants in order to observe what traits would carry on. He grew loads of peas and he counted them recording the differences. He learned that almost exactly 1/3 of the population of peas were different so he concluded that was a recessive trait. -
Plasmodium falciparum is described as the causative agent of malaria
Malaria is caused by the plasmodium parasite. The parasite can be spread to humans through the bites of infected mosquitoes. -
Hardy and Weinberg independently develop the Hardy-Weinberg equation for determining allele frequencies in populations
The Hardy-Weinberg equation states that p^2 + 2pq + q^2 = 1, where p^2 = frequency of dominant homozygotes (BB)
2pq = frequency of heterozygotes (Bb)
q^2 = frequency of recessive homozygotes (bb) And, according to the equation p + q = 1:
p = frequency of dominant allele (B)
q = frequency of recessive allele (b) -
T. Hunt Morgan discovers sex-linkage
A sex linkage is basically when a gene is located on one of the sex chromosomes instead of the other chromosomes (the autosomes). -
Neils Bohr develops the Bohr model of atom structure
The model is just a dense nucleus of protons and neutrons and a large area outside of electrons. Neutrons are located in the nucleus, whereas the electrons are on the outside. -
Frederick Griffith describes the process of transformation
He worked with two related strands of bacteria which cause pneumonia in mice. He discovered that when harmless live bacteria were mixed with heat-killed disease-causing bacteria and then injected into mice, the mice died. Griffith’s experiment led to the conclusion that genetic material could be transferred between cells. -
Avery, MacLoed and McCarty determine that DNA is the molecule that carries the genetic code
The bases = the code. There are 4 nucleotides in DNA (uracil, thymine, guanine, cytosine). Codons are units of 3 bases that code for an amino acid. Different codes create different sequences of amino acids. Amino acids are linked together to form different proteins which are the workhorses of the cell through which everything is carried out. -
Hershey-Chase experiments are published
Hershey and Chase concluded that DNA, not protein, functions as the T2 phages genetic material. They got to this conclusion by using radioactive sulfur which attaches to the T2's proteins making it easy to trace. The phosphorus attaches to the DNA and after they centrifuged it, they discovered traced or the radioactive DNA in the bacteria, but no protein. Meaning the phages kill bacteria by using their DNA. -
Rosalind Franklin works with DNA and X-Ray crystallography and develops “Image 51”
Franklin provided her X-ray crystallographs of the DNA molecule which showed that the molecule had the grooves on the outside of the molecule, not the opposite way as Watson and Crick thought. -
Watson and Crick propose the double helix model of DNA structure
Watson and Crick were the ones who built a model of the DNA molecule, and Rosalind Franklin took an x-ray photo of the molecule itself from above which displayed the double-helix shape. -
Meselson and Stahl work with DNA replication
The DNA melts (separate from each other) into two strands progressively. These strands act like a template for nucleotides to bind, following the rule of match G with C and A with T. As the strands melt, the nucleotides are polymerized by a polymerase and new DNA is synthesized. By the end of the process, the cell presents two copies of the genetic material. This event happens only when the cell is about to divide. -
Nirenberg cracks the genetic code
A specific sequence of genes that align up on the different chromosomes in the nucleus of a cell. Genes are composed of DNA molecules which are composed of molecules arranged in a specific order. These DNA molecules split and form patterns and other molecules to attach to and these molecules make different components utilized in the body. -
Endosymbiosis is described by Lynn Margulis
A theory that states that the mitochondria and chloroplasts contained within modern animal and plant cells were once free living bacteria that were engulfed by another bacterial cell leading to the eukaryotic cell. -
Apollo 11 lands on the moon
Apollo 11 was the 5th human spaceflight of the Apollo program, the 3rd human voyage to the moon, and the 1st manned mission to land on the Moon. It launched on July 16, 1969 and on July 21, 1969, Armstrong and Aldrin became the first humans to set foot on the Moon. -
Apollo 11 lands on the moon
Apollo 11 was the 5th human spaceflight of the Apollo program, the 3rd human voyage to the moon, and the 1st manned mission to land on the Moon. It launched on July 16, 1969 and on July 21, 1969, Armstrong and Aldrin became the first humans to set foot on the Moon. -
Spliceosomes were discovered and described
In mRNA processing, the spliceosomes binds to the mRNA to cut out introns, which are sections of the mRNA that are not necessary for translation. The spliceosomes is a special complex made up of proteins and small nuclear RNA molecules. -
The Sanger Technique is developed
A method of determining the location of a specific place of a DNA fragment, based on where synthesis of a new DNA chain stops. -
Deep sea hydrothermal vents and associated life around them are discovered
They proves that we only live on a very small layer of Earth. That at the depths that they are located, they are so close to the center of magma, whether there is a volcano or not, that they are able to produce unimaginable heat! They provide a healthy environment for lots of underwater organisms that where believed to be unable to live at such depths. -
Kary Mullis develops Polymerase Chain Reaction
PCR is a process that is done to take a little bit of DNA as well as the enzyme DNA polymerase and amplify (increase) the DNA sample. In short, it's a way to make more DNA from a small sample. -
CRISPRs/CAS 9 is identified and described
Bacteria in the body are able to defend themselves by cutting up pieces of DNA from invading viruses, storing them in the spaces in the bacteria’s own DNA and recognizing the viruses if they come back. This is known as Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR). -
The Innocence Project is founded
Convicts can ask the Innocence Project to help them prove their innocence if DNA evidence is available. -
Dolly the sheep is cloned
Mammary cells were removed from a 6 year old ewe in its last trimester of pregnancy. Cells were placed in culture dish and starved of nutrients to verge to death. A rescued cell was inserted into unfertilized sheep egg (containing no DNA). The egg thinks it's fertilized and embryo production begins. Egg implanted into ewe it's ready for pregnancy. After 148 days, Dolly was born. It took scientists 227 tries before producing Dolly. -
Sahelanthropus tchadensis fossil discovered
It was discovered by Ahounta Djimdoumalbaye in 2001 in Chad, in the southern Sahara desert. It lived sometime between 7 and 6 million years ago. -
Human genome is fully sequenced
It's about knowing all the sequence of the nitrogenous bases in DNA. Yes, some of these nitrogenous bases change. The project focuses on the ones that are common/true for every human. It's important because scientists want to cure diseases originated by genes, mismatched pairs, etc. So, if a disease is inherited, they can go to the human genome, compare it and see the difference and maybe find a cure. -
Richard L Bible is executed
Bible was convicted in the 1988 murder of Jennifer Wilson. While the little girl was on vacation with her family in Flagstaff, Bible kidnapped her, molested her, and then bludgeoned her to death.
He never admitted guilt. He died by lethal injection.
