Download 2a. Describe the discoveries that led to the modeling

p. 348 A.Q. 1a, 2ab, 3ab
p. 348 A.Q. 1a, 2ab, 3ab
1a. List the chemical components of DNA.
1a. The chemical components of DNA are
deoxyribose, phosphate groups, and four
different nitrogenous bases.
2a. Describe the discoveries that led to the
modeling of DNA.
2a. Chargaff discovered base pairing rules.
Franklin took X-ray photographs that revealed
that DNA has a spiral structure. This finding
helped Watson and Crick understand DNA’s
structure.
p. 348 A.Q. 1a, 2ab, 3ab
2b. Why did scientists have to use tools other than microscopes to solve the
structure of DNA?
2b. Scientists had to use tools other than microscopes because DNA is too
small to be seen with light microscopes, the only type available at the time.
3a. Describe Watson and Crick’s model of the DNA molecule.
3a. Watson and Crick’s model is composed of two strands that are connected
by bonds between nitrogen bases.
3b. Did Watson and Crick’s model account for the equal amounts of thymine
and adenine in DNA? Explain.
3b. Yes; Watson and Crick’s model depicted DNA as a double helix with
adenine and thymine paired together. This pairing accounts for the equal
amounts of thymine and adenine in DNA.