Name __________________________________
THE STRUCTURE OF DNA
DNA:
Period _______ Date ___________ Seat _____
Deoxyribonucleic acid, a nucleic acid. It is the main component of chromosomes and is involved in the storing,
copying, and transmitting of genetic information.
Nucleotide: The building blocks of nucleic acids.
Nucleotide Structure
DISCOVERIES THAT REVEALED THE STRUCTURE OF DNA
Erwin Chargaff’s rule: In DNA, the percentage of A = T,
and the percentage of G = C.
Phosphate
group
Nitrogenous
Base
Rosalind Franklin’s Photograph (X-ray diffraction technique)
Her photo revealed three things:
Sugar
(deoxyribose)
1. DNA has two strands
2. DNA is a double helix
3. The bases are near the center
Photo 51
Nitrogenous bases (four types in DNA)
Guanine
James Watson and Francis Crick (Nobel prize winners)
Watson & Crick figured out the
structure of DNA in 1953 by:
Purines
Adenine
Pyrimidines
1. Attending lectures
2. Asking questions
Cytosine
3. Building models
Pyrimidines
4. Seeing photo 51
Thymine
1
Name __________________________________
THE STRUCTURE OF DNA
Period _______ Date ___________ Seat _____
Double helix: Two strands twisted around each other resembling a
spiral staircase.
Base Pairing: The principle that bonds in DNA can form only between adenine (A) and thymine (T) and
between guanine (G) and cytosine (C).
Antiparallel Strands: Because the two strands in DNA run in opposite directions, any nucleotides that form
pairs must be upside down to each other.
Antiparallel strands
Phosphate group
Strong covalent bonds
Deoxyribose sugar
G’s bond with C’s
Weak hydrogen bonds
2
A’s bond with T’s