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Gregor Mendel recognized that pea plants had different characteristics and wanted to know why. In experimenting with different generations of plants, he deduced the basic laws of inheritance, and that genes are passed from the parent plants to the offspring, one from each parent. He also worked with recessive and dominant traits Image from: http://www.themarysue.com/pea-plant-lung/
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Friedrich Miescher took white blood cells from the puss he had collected from patients infections and recognized that they all contained a portion which he called "nuclein". He recognized the unique ratio between nitrogen and phosphorus that he found in the "nuclein" inside the nucleous. He thought that this was a phosphorus storehouse for the cell. Image from: http://www.dnaftb.org
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Mendel’s ideas were verified by Carl Correns, Hugo de Vries, and Erich Von Tschermak-Seysenegg
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Thomas Hunt Morgan worked with the fruit fly, Drosophila melanogaster, and confirmed that traits are contained in genes on chromosomes by studying the mutations that occured on fruit flies (also confirmed Mendel's theory) Image from: http://www4.ncsu.edu/~ndsingh/html/publications.html
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Phoebus Levene identifies the base, sugar, and phosphate nucleotide unit of DNA- Most well known for his tetranucleotide theory of DNA, which turned out to be incorrect.
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Barbara McClintock worked with corn. She performed numberous experiments with them and map their chromoseomes. She developed the "one enzyme, one gene theory" and received a nobel prize in 1983. Image from: http://www.nobelprize.org/nobel_prizes/medicine/laureates/1983/mcclintock-photo.html
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George Beadle and Edward Tatum worked with the mold, Neurospora, that grows on bread. They discovered that this mold requires enzymes and vitamins to grow and that when mutations occured, the synthesis pathway to create the necessary enzymes was disrupted. From this, they learned how to synthesize enzymes that control basic metabolic processes. image from: https://www2.estrellamountain.edu/faculty/farabee/BIOBK/BioBookPROTSYn.html
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Joshua Lederberg- how DNA gets from one organism to another
He worked with E. coli mutants and proved bacterial conjugation (DNA from one organism transfering to another) occurred. Lederberg, Edward Tatum, and George Beadle all shared the 1958 Nobel Prize. Image from: http://parts.igem.org/DNA/Conjugation -
Erwin Chargaff recognized that there may be more to DNA than only tetranucleotide blocks as Phoebus Levene suggested. He measured levels of the four nucleotide blocks and realized that very similar levels of Adenine and Thymine existed in every organism he tested, and very similar levels of Guanine and Cytosine existed in the same organisms tested. This proved that Levene was incorrect. Image from: http://cyberbridge.mcb.harvard.edu/dna_1.html
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Rosalind Franklin and the x-ray used to see unique “pattern” projected by DNA onto photographic film. She figured out the basic demensions of a DNA strand and concluded that DNA was probably in a helical structure (she did not get a lot fo credit for this because Crick and Watson submitted their information around the same time and they claimed all the credit) Image from: https://askabiologist.asu.edu/Rosalind_Franklin-DNA
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This experiment showed that DNA is the only element needed for viral replication.They used T2 bacteriophage to show this. Image form: http://www.themadscienceblog.com/2013/10/gender-bias-in-science-part-iv-martha.html
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Linus Pauling proposed a triple-stranded helix structure that ended up being very incorrect. He proposed that the phosphates make the core and the bases point outwards. This is now known to be impossible because the negatives in the phosphates would repel eachother and the sturcture would not hold together. Image from: https://www.msu.edu/course/lbs/333/snapshot.afs/fall/pauling.html
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Francis Crick and James Watson discovered that DNA had a double helix structure and in 1963 received a nobel prize. Image from: http://www.nature.com/scitable/topicpage/discovery-of-dna-structure-and-function-watson-397
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Arthur Kornberg used E. coli to isolate DNA polymerase (enzyme that synthesizes DNA) which he then used to prove that DNA is constructed in one direction. Image from: https://www.neb.com/tools-and-resources/feature-articles/anatomy-of-a-polymerase-how-structure-effects-function
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Roy Britten discovered repetitive DNA in eukaryotic organisms Image from: https://www.caltech.edu/news/roy-j-britten-92-2046
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Stanley Cohen and Herbert Boyer discovered recombinant DNA which proved that genetically engineered DNA can be cloned in forein cells. Image from: http://lemelson.mit.edu/winners/herbert-boyer-and-stanley-cohen
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Frederick Sanger discovered how to sequence DNA. It is separated into two strands, copied with chemicallys altered bases, and then put back together int he same order of the original DNA stand. He got a nobel prize in 1951. Image from: http://www.nobelprize.org/nobel_prizes/chemistry/laureates/1958/sanger-bio.html
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While attempting to discover how inhertited diseases pass from one generation to another and failing miserably, he developed the first DNA fingerprint, a technique that has now been refined and is used to catch criminals. Image from: http://aboutforensics.co.uk/sir-alec-jeffreys/
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DNA was used to exonerate an innocent man, Richard Buckland, and to convict the true criminal Colin Pitchfork. Image from: http://www.slideshare.net/RioneDrevale/dna-fingerprinting-30483502
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First case where DNA was used in the US. It was used to convict Tommy Lee Andrews of rape (his DNA profile matched semen) Image from: http://articles.orlandosentinel.com/2012-10-22/news/os-tommie-lee-andrews-rape-hearing-20121022_1_dna-evidence-treatment-facility-tommie-lee-andrews
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Steve Fodor created the first gene chip. A gene chip is a DNA microarroy and allows scientists to measure large numbers of genes all at one time, and to genotype many regions of a genome all at one time. Image from: https://www.dkfz.de/gpcf/affymetrix_genechips.html
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Pat Brown worked with DNA arrangement and why genes do what they do, like cause heritable diferences and what they do dynamically.
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The human genome project after 13 years (two years ahead of schedule) was an international effort to map the entire human genome. Image from: http://www.davidstreams.com/mis-apuntes/human-genome-project/
