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/
Friedrich Miescher and "nuclein"
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
Verification of Mendel
Mendel’s ideas were verified by Carl Correns, Hugo de Vries, and Erich Von Tschermak-Seysenegg
Thomas Hunt Morgan and his fruit flies
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
Phoebus Levene incorrectly identifies DNA bases
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.
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
Joshua Lederberg and how DNA gets from one thing to another
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
Rosalind Franklin uses the x-ray to see unique patterns of DNA
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
Alfred Hershey and Martha Chase Blender Experiment
Linus Pauling proposes the idea of a triple-strand helix structure
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
Francis Crick and James Watson discover double helix
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/
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
Pat Brown worked with DNA arrangement and why genes do what they do, like cause heritable diferences and what they do dynamically.