1. 2.6 & 7.1 DNA & RNA Structure Notes
IB Biology HL 1
Mrs. Peters
Spring 2015

2. DNA DNA: deoxyribonucleic acid
Molecular basis of inheritance, genetic material

3. DNA
Structure discovered by James Watson and Francis Crick in April 1953
their model was based on Rosalind Franklin’s x-ray data and Edwin Chargaff’s nucleotide data

4. RNA RNA: ribonucleic acid DNA “photocopy”
leaves nucleus to make proteins

5. U1. Nucleic Acids
Nucleic Acids: type of macromolecule made up of nucleotides (monomers)
Two types:
DNA: Deoxyribonucleic Acid
RNA: Ribonucleic Acid
Ibbiologyhelp.com

6. U1. Nucleotide Structure
Phosphate group
Pentose Sugar
DNA: deoxyribose
RNA: ribose
Nitrogen base
DNA (A,C,G,T)
RNA (A,C,G,U)
Held together by covalent bonds
Ibbiologyhelp.com

7. S1. Nucleotide Structure Diagrams
Draw and label a nucleotide (in class)
Ibbiologyhelp.com

8. U2. DNA vs. RNA (In Class) Feature DNA RNA Strand Double helix
Single strand
Pentose Sugar
Deoxyribose
Ribose
Nitrogen Bases
A, C, G, T
A, C, G, U
Location
Nucleus only
Nucleus and cytoplasm

9. U3. DNA Structure Nitrogen Bases Purines: adenine (A), guanine (G)
Two rings
Pyrmidines: cytosine (C), thymine(T)
One ring

10. U3. DNA Structure Complementary Base Pairing:
A and T bonded by two H bonds
C and G bonded by three H bonds

11. U3. DNA Structure
Two nucleotides are bonded together in the center by hydrogen bonds forming a double helix
Sugar and phosphate are covalently bonded, forming the “backbone” of each strand

12. U3. DNA Structure
Double helix is made of two separate strands which are antiparallel
5’- 3’
3’-5’ (upside down)
5’ end: phosphate group (PO43-)
3’ end hydroxide group (–OH) attached to sugar

13. U3. DNA Structure
Draw and label a diagram of the molecular structure of DNA

14. DNA Structure
Describe what is meant by the statement: “The structure of DNA is described as a twisted ladder.”

15. 7.1 U2. Nucleosomes Nucleosomes help to supercoil DNA
8 histone proteins (octomer) with DNA wrapped around twice
H1(specific histone protein) attaches the DNA to the octomer
Linker DNA- short segment of DNA connects one nucleosome to another
Beyondthedish.wordpress.com

16. 7.1 S1. Hershey and Chase
1950’s Alfred Hershey and Martha Chase studied viruses to determine if genetic material was protein or DNA
DNA contains phosphorous, proteins contain sulfur
Used radioactive isotopes of phosphorous-32 and sulfur-35 in T2 bacteriophages (virus) which were injected into E. coli (bacteria)

17. 7.1 S1. Hershey and Chase Trial 1:
Injected bacteria with T2 viruses that contained sulfur-35 in protein coats (on the outside) and normal DNA
Used blender the gently shake the virus off the bacteria
Bacteria produced no radioactivity, virus had the radioactive isotopes still attached

18. 7.1 S1. Hershey and Chase Trial 2:
Injected bacteria with T2 viruses that contained phosphorous-32 in DNA, normal protein coats
Used blender to gently shake virus off bacteria
Bacteria produced radioactive DNA

19. 7.1 S1. Hershey and Chase Conclusion:
DNA is the genetic material because the virus DNA had radioactive phosphorous which became present in the bacteria’s DNA

20. 7.1 S1. Hershey and Chase

21. 7.1 A1: Franklin and Wilkins
Rosalind Franklin was a research associate in biophysics unit at King’s College in London.
Became skilled in techniques of crystallography and X-ray diffraction while researching other carbon compounds.
Created the sharpest X-ray diffraction images of DNA in existence
Through rigorous analysis of the patterns, she calculated the dimensions of the DNA helix

22. 7.1 A1: Franklin and Wilkins
Maurice Wilkins worked in the biophysics unit at King’s College also.
He also used X-ray diffraction to look at DNA
Shared Franklin’s diffraction pattern and calculations to Watson, without Franklin’s knowledge or permission, before she could publish her findings.

23. 7.1 A1. Franklin and Wilkins Deductions made by Franklin:
Cross in the center indicated a helix shape
Angle of the cross shape showed the pitch of the helix
Distance between horizontal bars shows the turn (3.4 nm apart)
Undsci.berkeley.edu

24. 7.1 A1. Franklin and Wilkins Deductions made by Franklin:
Distance between middle of pattern and top shows repeating structure
Distance is 0.34 nm between repeats

25. DNA Structure Review What are the components of DNA?
How is 6 ft of DNA stored in every cell?