Discovery Of DNA Flashcards
Who was the first person to identify DNA?
Friedrich Miescher (1869, Swiss biochemist)
Describe the contributions of Friedrich Miescher
He was the first to identify DNA. Noted the presence of phosphorus in DNA using pus cells in discarded bandages.
Discovered that the nuclei of cells contain large quantities of a substance that does not act like protein (nuclein).
Who discovered the process of DNA transformation?
Freferick Griffith (1920s)
Describe the contributions of Frederick Griffith
While trying to develop a vaccine for streptococcus pneumoniae, he found observations which showed that protein is not the hereditary material.
He founded transformation and identified DNA as the transforming substance.
Describe the 1928 experiment which led to the discovery of transformation
Frederick Griffith.
Injected virulent pneumonia into a mouse and the mouse died. Next, he injected the non-virulent pneumonia into a mouse and the mouse lived. Then, he heated the virulent disease to kill it and injected the mouse, and the mouse lived. Last, he injected non-virulent pneumonia into the heated pneumonia and the mouse died.
Who discovered that hereditary information is stored in the nucleus?
Hammerling (1930s)
Describe Hammerling’s experiment
Worked with two forms of a single-celled green alga called Acteabularia. He removed the cap from the cells and the foot from others. He found that if the cap was removed, they regenerated new caps, but if the foot was removed no regeneration occurred.
Found that the entire genetic complement is stored in the nucleus of eukaryote.
Describe the contributions of Avery, Macleod, and McCarty (1944)
Separated dead virulent cells into fractions and coinjected them with the avirulent strain to see which fraction contained the transforming principle.
They discovered this fraction was DNA.
Describe the contributions of Chargaff (1949)
Founded “Chargaff’s Rule” which states: %A = %T and %C = %G
Who proved the correlation between DNA and genetic information?
Hershey and Chase (1952)
Describe the 1952 “blender experiment”
Hershey and Chase.
Side-by-side experiments are performed with separate bacteriophage cultures in which either the protein capsule is labeled with radioactive sulfur or the DNA core is labeled with radioactive phosphorus.
The labeled phases are allowed to infect bacteria.
Agitation in a blender dislodges phage particles from bacteria cells.
Centrifugation concentrates cells, separating them from the phage particles left in the supernatant.
Sulfur was found predominantly in the supernatant.
Phosphorus was found predominantly in the cell fraction, from which a new generation of infective phage can be isolated.
Therefore, the active component of the bacteriophage that transmits the infective characteristic is the DNA.
Who discovered that DNA is in the shape of a double-helix?
Rosalind Franklin
Describe the contributions of Rosalind Franklin
Produced an X-ray diffraction pattern of DNA that suggested it was in the shape of a double-helix. Her work laid the foundation for Watson and Crick
Who proposed the modern structure of DNA?
Watson and Crick (1953)
Describe the Watson-Crick model of DNA
A DNA molecule consists of two polynucleotide strands coiled around each other in a helical “twisted ladder” structure. The sugar-phosphate backbone is on the outside nad the bases are on the inside. The two strands run in opposite directions (antiparallel), one in the 5’ to 3’ direction, the other 3’ to 5’
