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Gregor Mendel
Gregor Mendel bred pea plants to figure out why some pea plants are purple and some are white. He self pollinated generation P- which was composed to one purple plant and one white plant. The offspring were all purple and all white. After he self pollinated those, he cross pollinated their offspring and that generation became known as the F1 generation. The F1 generation was all purple. Mendel then cross pollinated the F1 generation to get the F2 generation which was 3/4 purple and 1/4 white. -
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Genetics Timeline
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Gregor Mendel's Contribution
After conducting his pea plant experiment, Mendel found that genes have alternate forms, named dominat and recessive alleles. He also found that each characteristic has two genes, one from each parent. Mendel also found that sperm and egg each carry one allele, and they spererate before gamete production. -
William Bateson and Reginald Punnett
Bateson and Punnett crossed two purple flowers with long pollen together after rediscovering Mendel's laws. Their results were- Purple Long- 284, Purple Round- 21, Red Long- 21, Red Round- 55. This resulting in the discovery of linked genes, which is the recombination of genes. Bateson also coined the term Epistasis and Punnett founded Punnett Squares. -
Thomas Hunt Morgan
Morgan crossesd thwo fruit flies, one with a gray body and long wings, and one with a black body and vestigal wings together. This lead to Morgan mapping genes. Morgan also was interested in why white eyes only occured in males, and found that the white eyes were a sex-linked trait, Thomas Hunt Morgan is also noted on finding the difference between parental and recombinat genes. -
Archibald Garrod
Garrod hypothesised the "One Gene, One Enzyme" theory. He studied Alkaptonuria- a diesease that effects metabolism. He discovered that people suffering from Alkaptonuria lack an enzyme in the metabolism, confirming his "One Gene, One Enzyme" theory. He is considered to be the father of chemical genetics. -
Frederick Griffith
Griffith worked at the Ministry of Health in London, working with single celled bacteria. Griffith used lethal and non-lethal pneumonia.The lethal killed the mice, while the non-lethal didn't. Griffith then heated the lethal pneumonia, which did not kill the mouse. Griffith then mixed the heated lethal with the normal temperature non-lethal, which killed the mouse. -
Frederick Griffith Results
Griffith found that the non-lethal strain was able to acquire the lethal qualities, resulting in the discovery of transformation. -
George Beadle and Edward Tatum
Beadel and Tatum cultured normal bread mold, and crossed it with mutated bread mold that they grew. They found that some of the mutant spores could not replicate without the addition of the amino acid arginine. This reiterated Garrod's "One Gene, One Enzyme" theory. -
Erwin Chargaff
Erwin Chargaff found that adenine is always paired with thymine and guanine always pairs with cytosine. A=30.9% T= 29.4% G=19.9% and C=19.8%. These later became known as Chargaff's Rules. -
Maurice Wilkins and Rosalind Franklin
Wilkins and Franklin used crystallographic x-ray to photograph DNA which ultimately led to the discovery of DNA being a helix. -
Alfred Hershey and Martha Chase
Hershey and Chase used radioactive phages to see if DNA was genetic. Step 1: Mix the radioactive phages with bacteria, and let the phages infect the bacteria 2:using a blender, agitate the phages to seperate the outside and inside ofthe bacteria cells 3:Centrifuge the mixture 4: Measure the amount of radioactivity in the pellet and liquid. This lead to the understanding that DNA was genetic. -
James Watson and Francis Crick
Using Maurice Wilkins and Rosalind Franklin's picture of DNA, Watson and Crick found that DNA is a double helix. The first model they created out of wire did not work though, so they then constructed a model putting the nitrogen bases into ann exact order. They found that DNA has a 2 nm diameter and there are 2 polynucleotides. -
Marshall Nirenberg
Nirenberg added RNA to a E.Coli free cell. He then added DNase, which breaks DNA down so that no new proteins would be produced. He then added one radioactive amino acid and 19 unlabeled amino acids. The protein turned out to be radioactive. This led to Nirenberg finding the genetic code for phenylalaine, and translatign the genetic code.
