17 terms

Chapter 5: DNA and Chromosomes

4 different nucleotides
2 purines and 2 pyrimidines
2 purines
Adenine and guanine
2 pyrimidines
Cytosine and thymine
Griffith (1928)
Transformation experiments
Avery, McCarty, MacCleod (1943)
isolate the transforming agent and identify it as DNA
L. Pauling & Robert Corey (1948)
discovered many proteins have an alpha helical structure (model building & crystallography)
Chargaff (1950)
adenine = thymine; cytosine=guanine
Hershey and Chase (1952)
show that DNA of virus is part that enters host cell
William Astbury (1938)
from DNA x-ray crystallography conclude bases lie flat ("stacked like pennies") and are spaced 3.4A apart
Sven Furburg (~1950)
making models of DNA shows sugars are at right angles to bases
Jerry Donahue (1953)
tells Watson bases would be in the keto form as opposed to the enol
Rosalind Franklin (1951)
did X ray crystallography of DNA w/ student Raymond Gosling
James Watson & Francis Crick
Model Building based on available experimental data
L. Pauling & Robert Corey
Model Building and X-ray
Rosalind Franklin's data
2 forms A (dry) & B (wet); phosphates on the outside; for B form: confirmed that the bases were 3.4A apart, 10 bases per turn, thus 34 A per turn, and helical structure (likely 2 strands)
Watson & Crick make a key intuitive leap in construction of their model
Strands are anti-parallel and complementary base pairing is the key to copying
Eucaryotic Chromosome Structure
Chromatin; chromosome; changes in degree of packaging of DNA at different times of the cell cycle; 3 structurally significant sequences (Replication origin, centromeres, and telomeres)