Genetics Timeline

Gregor Mendel

Apr 5, 1866

Experiment:
cross-fertilized pea plants
1. Removed stamens from purple flower
2. Ttransferred pollen from stamens of white flower to carpel of purple flower
3. Pollinated carpel matured into pod
4. Planted seeds from pod Contribution
-different alleles
-two genes, one from each parent
-allele pairs separate during meiosis
-one allele fully expressed, other no noticeable effect

William Bateson and Reginald Punnett

Apr 5, 1908

Experiment:
crossed doubly heterozygous plants that exhibited the dominant traits (purple flowers and long pollen grains) the corresponding recessive traits are red flowers and round pollen.
Contribution
-discovered linked genes

Thomas Hunt Morgan

Apr 5, 1915

Experiment:
Cross between a wild type fruit fly and a fly with a black body and vestigial wings (test cross)
Contribution:
-discovered crossing over and genetic recombination

Archibald Garrod

Apr 5, 1925

Experiment:
observed that when exposed to air, the patients with alkaptonuria's urine turns dark which lead to his conclusion that alkaptonuris is a congenital disorder.
Contribution:
-inherited disease reflects a person's inability to make a particular enzyme

Frederick Griffith

Apr 5, 1928

Experiment:
Used mice to determine which bacteria would kill them
Contribution:
-discovered tranformation

George Beadle and Edward Tatum

Apr 5, 1941

Experiment:
Used orange bread mold which was unable to grow on the usual simple growth medium
Contribution:
-one gene-one enzyme (the function of an individual gene is to dictate the production of a single enzyme.

Erwin Chargaff

Apr 5, 1949

Experiment:
Noticed a pattern in the model that he made. Toook sample of different DNA cells to find out A=T and C=G.
Contribution:
-amount of adenine=amount of thymine
-amount of cytosine=amount of guanine
-base-pairing rules

Alfred Hershey and Martha Chase

Apr 5, 1952

Experiment:
-Used bacteriophage composed of only DNA proteins
-DNA tagged by radioactive phosphorus and protein was tagged with radioactibe sulfur
Contribution:
-determined DNA was genetic material

Maurice Wilkins and Rosalind Franklin

Apr 5, 1952

Experiment:
-took a photograph of DNA
Contribution:
-DNA was a helix

James Watson and Francis Crick

Apr 5, 1953

Experiment:
-used wire models, tried putting the backbones on the outside and forcing the nitrogenous bases to swivel to the interior of the model
Contribution:
-DNA was a double helix made of 2 polynucleotide strands

Marshall Nirenberg

Apr 5, 1961

Experiment:
-set up a "cell free system" with "sap" from E. coli cells containing enzymes and an energy system
-added simple chains of RNA and amino acids
Contribution:
-discovered first "triplet"- sequence of three bases of DNA codes for one of the 20 amino acids that serve as building blocks of protein