2. 30 November 2015 1 Page 87 Objective: I know the structure and function of DNA (deoxyribonucleic acid) Title: The Structure of DNA DNA: What is the end result of Meiosis?

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4. 3 DNA DNA.DNA is often called the blueprint of life. In simple terms, DNA contains the instructions for making proteins within the cell.

5. 4 Watson & Crick’s Model

6. 5 DNA Why do we study DNA? all life on Earth has DNA, medical benefits such as cures for diseases, better food crops.

7. 6 Chromosomes and DNA Our genes are on our chromosomes. Chromosomes are made up of a chemical called DNA.

8. 7 The Shape of the Molecule DNA is a very long polymer. The basic shape is like a twisted ladder or zipper. This is called a double helix.

9. 8 The Double Helix Molecule The DNA double helix has two strands twisted together.

10. 9 One Strand of DNA The backbone of the molecule is alternating phosphates and deoxyribose sugar The teeth are nitrogenous bases. phosphate deoxyribose bases

11. 10 Nucleotides CC C O Phosphate O C C O -P O O O O O O O One deoxyribose together with its phosphate and base make a nucleotide. Nitrogenous base Deoxyribose

12. 11 One Strand of DNA One strand of DNA is a polymer of nucleotides. One strand of DNA has many millions of nucleotides. nucleotide

13. 12 Four nitrogenous bases Cytosine C Thymine T Adenine A Guanine G DNA has four different bases:

14. 13 Thymine and Cytosine Thymine and cytosine each have one ring of carbon and nitrogen atoms.Thymine and cytosine each have one ring of carbon and nitrogen atoms. C C C C N N O N cytosine C C C C N N O O thymine C

15. 14 Adenine and Guanine Adenine and guanine each have two rings of carbon and nitrogen atoms.Adenine and guanine each have two rings of carbon and nitrogen atoms. C C C C N N N Adenine N N C C C C C N N O N Guanine N N C

16. 15 Two Stranded DNA Remember, DNA has two strands that fit together something like a zipper. The teeth are the nitrogenous bases but why do they stick together?

17. 16 C C C C N N O N C C C C N N O N N N C Hydrogen Bonds The bases attract each other because of weak hydrogen bonds.

18. 17 Chargraff’s Rule: Adenine and Thymine always join together A T Cytosine and Guanine always join together C G

19. 18 DNA by the Numbers 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 m or 93 million miles from the sun.

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