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Gregor Mendel
Experiment: used self pollinared peas to ensure they were true-breeding (known as P generation), then he cross pollinated the P generation (known as F1 generation), the F1 were allowed to self pollinate (known as F2 generation) Contribution: discovered that parents pass on to their offspring discrete heritable facotrs (genes). Stressed that genes retain their individuality after generation. -
William Bateson and Reginald Punnett
Experiment: crossed doubly heterozygous plants that exhibited the dominant traits, purple flowers and long pollen grains. The corresponding recessive traits are red flower and round pollen. Contribution: Discovered linked genes- genes that are located close together on the same chromosome -
Thomas Hunt Morgan
Experiment: mated a gray fly with long wings with a black fly witih vestigial wings and performed a testcross Contribution: Discovered crossing over and genetic recombination -
Archibald Garrod
Experiment: exposed patients' urine with alkaptonuria to sunlight Contribution: Discovered that genes dictate phenotypes through enzymes -
Frederick Griffith
Experiment: experimented on a species of bacterium that causes pneumonia. Studied 2 varieties of the bacterium, a pathogenic (disease-causing) one and a carient that was harmless. results were that pathogenic + heat =mouse not killed, (heat + pathogenic) + varient = killed mouse. Contribution: Discovered transformation. -
George Beadle and Edward Tatum
Experiment: irradiated a large number of Neurospora, and produced some organisms with mutant genes. Then they crossed the potential mutants with non-irradiated Neurospora. Contribution: came up with the one gene- one polypeptide theory -
Erwin Chargaff
Experiment: He took samples of DNA of different cells and found that the amount of adenine was almost equal to the amount of thymine, and that the amount of guanine was almost equal to the amount of cytosine Contribution: Discovered base pairing rules-adenine bonds with thymine and cytosine bonds with guanine -
Alfred Hershey and Martha Chase
Experiment: used bacteriophage composed of only DNA and Protein was tagged with radioactive sulfur Contribution: Determined that DNA was the genetic material -
Rosalind Franklin and Maurice Wilkins
Experiment: took and x-ray crystallographic photograph of DNA and observed it Contrubution: Discovered DNA was a helix -
James Watson and Francis Crick
Experiment:built three-dimensional models, using cardboard cutouts and sheet metal to represent the molecule's chainlike structure. Contribution: determined that DNA was a double helix made of 2 polynucleotide strands and the diameter of DNA= 2 nm and nitrogen bases were 0.33 nm apart -
Marshall Nirenberg
Experiment: produced RNA comprised solely of uracil. Then he added it into a cell-free extract of Escherichia coli for protein synthesis. Then he added DNase so that no more proteins would be produced other than that from their synthetic RNA. Then he added 1 radioactively labeled amino acid, the building blocks of proteins, and 19 unlabeled amino acids to the extract, varying the labeled amino acid in each sample Contribution: synthesized the amino acid phenylalanine using the PNA codon UUU
