History and Discovery of DNA Flashcards
(12 cards)
Who was the first to isolate DNA?
J. Frederich Miescher in 1869
He called it nucleic acid due to its acidic nature and location in the nucleus.
What did scientists discover in the 1920s regarding chromosomes?
Chromosomes contained DNA and some suggested DNA was hereditary material
This was a significant step in understanding the genetic role of DNA.
What are the two types of nucleic acids discovered by Phoebus Levene?
RNA and DNA
They differ by one oxygen atom and are made of chains of nucleotides.
What components do both DNA and RNA contain?
5 ring carbon sugar, phosphate group, and one of four nitrogen bases
The bases for DNA are A (adenine), T (thymine), G (guanine), C (cytosine); RNA contains U (uracil) instead of thymine.
What process did Frederick Griffith discover in 1928?
Transformation
He concluded that a factor from dead smooth bacteria transformed live rough bacteria into a smooth strain.
What did Avery, McCarty, and MacLeod identify in 1944?
The transforming factor in Griffith’s experiment as DNA
They demonstrated that DNA was the substance of heredity.
What was the result when heat-killed pathogenic bacteria were treated with a protein-destroying enzyme?
Transformation still occurred
This indicated that protein was not the transforming factor.
What was the result when heat-killed pathogenic bacteria were treated with a DNA-destroying enzyme?
Transformation did not occur
This provided evidence that DNA was essential for transformation.
What did Chargaff discover in 1951?
The nitrogen base ratio in cells is related to the genetic code
Specifically, the number of adenines equals the number of thymines and the number of cytosines equals the number of guanines.
What technique did Rosalind Franklin use to study DNA?
X-ray crystallography
She found a pattern of repeating structures in DNA.
What did Hershey and Chase discover in 1952?
That DNA, not protein, was the transforming factor in Griffith’s experiment
They used radioactive tracers to show that DNA entered bacteria.
What significant structure did Watson and Crick discover between 1953 and 1964?
The 3-D structure of DNA, known as the double helix
They also uncovered the DNA code.
