1. DNA Structure - Part 1

2. Learning Objectives
Describe the overall structure of the DNA molecule

3. Chromosomes and DNA
Chromosomes are made up of DNA and protein. A gene is a sequence of DNA found in chromosomes.

4. DeoxyriboNucleic Acid
All life on earth uses DNA to carry its genetic code or blueprint.

5. DNA DNA is often called the blueprint of life
DNA contains the instructions for making proteins

6. Watson and Crick’s Model
With the help of Rosalind Franklin’s X-ray diffraction image, Watson and Crick discovered the structure of DNA

7. DNA Double Helix Structure
YouTube Video
DNA Double Helix Structure

8. The Shape of the DNA Molecule
DNA is a very long polymer
The basic shape is like a twisted ladder called a double helix
The DNA double helix has two strands twisted together

9. Structure of DNA
The DNA backbone is made of alternating phosphates and deoxyribose sugar
The rungs are nitrogenase bases
Bases
= Deoxyribose Sugar
= Phosphate

10. One Strand of DNA DNA is made of monomers called nucleotides

11. Nucleotide Phosphate Nitrogenous Base Deoxyribose Sugar
One deoxyribose sugar, one phosphate and one nitrogenous base make a nucleotide.

12. YouTube Video
DNA Structure

13. DNA Structure Amoeba Sisters
YouTube Video
DNA Structure Amoeba Sisters

14. Stop Here

15. DNA Structure - Part 2

16. Learning Objectives
Explain how bonds are formed between nitrogenous bases

17. Nucleotide Phosphate Nitrogenous Base Deoxyribose Sugar
One deoxyribose sugar, one phosphate and one nitrogenous base make a nucleotide.

18. Nitrogenous Bases
DNA has two different types of nitrogenous bases - pyrimidines and purines.

19. Purines and Pyrimidines
Cytosine (C)
Thymine (T)
Purines:
Adenine (A)
Guanine (G)

20. Chargaff’s Rule = = # of # of
Chargaff’s Rule - In DNA, the amount of G is equal to C and the amount of A is equal to T

21. Base Pairing
Adenine is paired to Thymine and Guanine is paired to Cytosine

22. Two Strands of DNA
DNA has two strands of DNA that fit together like a zipper
The teeth of the zipper are the nitrogenous bases
How do the two strands stick together?

23. Hydrogen Bonds Guanine Cytosine Adenine Thymine
The nitrogenous bases are attracted to each other because of hydrogen bonds.

24. Why Study DNA? Medical benefits such as cures for diseases
Better food crops
Central importance to all life on earth

25. What is DNA and How Does it Work?
YouTube Video
What is DNA and How Does it Work?

26. Stop Here

27. DNA Facts Each cell has about 2 meters of DNA
The average human has 75 trillion cells
The average human has enough DNA
to go from the earth to the sun more
than 400 times.
The earth is 150 billion meters from the sun

28. Summary of DNA Structure
Nucleotide: deoxyribose sugar, phosphate and nitrogenous base
Adenine - Thymine
Guanine - Cytosine
A - T G - C
Hydrogen bonds
hold DNA strands
together
Nucleotides joined together make up a strand of DNA.