1. Warm Up Analyze how science can change.
Compare and Contrast DNA and RNA.

2. RNA DNA BOTH ribose (sugar) Deoxyribose (sugar) Nitrogenous base:
uracil
Deoxyribose (sugar)
Nitrogenous base:
Thymine
Nucleic Acids
Made of nucleotides:
a five-carbon sugar
a phosphate group
a nitrogenous base
Flexible
Nitrogenous bases:
Adenine
Guanine
Cytosine
thymine
Stable

3. Analyze DNA and the Chart What do you notice?
Base
Number A T G C

4. Chargaff’s
Rule
C = G
T = A

5. Bases are bonded with Hydrogen bonds. A and T G and C
Two hydrogen bonds
G and C
Three hydrogen bonds

6. What the Difference? C and T and U A and G Pyrimidine Bases
Purine Bases
What the Difference?

7. Drawing Conclusions If A=T and G=C then Purines = Pyrimidines
A Purine always bonds with a Pyrimidine

8. Double Helix
DNA is formed by two strands of nucleotides.

9. How do scientists know?? Wilkins used x-ray diffraction.
Watson and Crick used data
collected by Wilkins and Chargaff.
Built a model.

10. SO…….
Science Changes
Scientists use each other research?
YES!!!!

11. Scientists work together to solve problems. Science Changes
New knowledge
modifications to current knowledge.
Individuals and teams have contributed and will continue to contribute to science.
Scientists conduct investigations for a many reasons:
exploration of new areas
discovery of new aspects of the natural world
confirmation of prior investigations

12. DNA Structure
DNA often is compared to a
twisted ladder.
Rails of the ladder are represented by the alternating deoxyribose and phosphate.
The pairs of bases (cytosine–guanine or thymine–adenine) form the steps.

13. Orientation
Position, direction
Parallel
Antiparallel

14. Orientation Of DNA Antiparallel
On the top rail, the strand is said to be oriented 5′ to 3′.
The strand on the bottom runs in the opposite direction and is oriented 3′ to 5′.

15. Chromosome Structure
To fit in a cell DNA coils tightly around histones(proteins)
Forms nucleosomes,
coil to form chromatin fibers.
chromatin fibers supercoil to form chromosomes

16. Describe the structure of DNA using the following words:
Double helix
Purine
Pyrimidine
Phosphate
deoxyribose

17. DNA is a nucleic acid made up of a phosphate, deoxyribose sugar, and nitrogeneous bases. Purine and pyrimididine bases pair up and coil tightly to for a double helix.

18. Word Wall