2. DNA (Deoxyribonucleic Acid)

3. Mr. Coleman Biology

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

5. Genetic material of cells… GENES – units of genetic material that CODES FOR A SPECIFIC TRAITGENES – units of genetic material that CODES FOR A SPECIFIC TRAIT Called NUCLEIC ACIDSCalled NUCLEIC ACIDS DNA is made up of repeating molecules called NUCLEOTIDESDNA is made up of repeating molecules called NUCLEOTIDES

6. A HISTORY OF DNA DNA double helixDiscovery of the DNA double helix A. Frederick Griffith – Discovers that a factor in diseased bacteria can transform harmless bacteria into deadly bacteria (1928) B.Rosalind Franklin - X-ray photo of DNA. (1952) C.Watson and Crick - described the DNA molecule from Franklin’s X-ray. (1953)

7. DNA Why do we study DNA? We study DNA for many reasons, e.g., its central importance to all life on Earth, medical benefits such as cures for diseases, better food crops.

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

9. 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.

10. The Double Helix Molecule The DNA double helix has two strands twisted together. (In the rest of this unit we will look at the structure of one strand.)

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

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

13. One Strand of DNA The backbone of the molecule is alternating phosphate and deoxyribose. The teeth are nitrogenous bases. phosphate deoxyribose bases

14. Nitrogenous Bases PURINESPURINES Adenine (A) 1.Adenine (A) Guanine (G) 2.Guanine (G) PYRIMIDINESPYRIMIDINES Thymine (T) 3.Thymine (T) Cytosine (C) 4.Cytosine (C) T or C A or G

15. Two Kinds of Bases in DNA Pyrimidines are single ring bases.Pyrimidines are single ring bases. Purines are double ring bases.Purines are double ring bases. C C C C N N O N C C C C N N N N N C

16. Thymine and Cytosine are pyrimidines 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

17. Adenine and Guanine are purines 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

18. 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?

19. 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 hydrogen bonds. Hydrogen bonds are weak but there are millions and millions of them in a single molecule of DNA.

20. Hydrogen Bonds, Hydrogen Bonds, cont. When making hydrogen bonds, cytosine always pairs up with guanine, And adenine always pairs up with thymine. C C C C N N N N N C C C C C N N O O C

21. BASE-PAIRINGS CG H-bonds T A

22. Chargaff’s Rule Adenine ThymineAdenine must pair with Thymine GuanineCytosineGuanine must pair with Cytosine about the sameTheir amounts in a given DNA molecule will be about the same. G C TA

23. Important: Adenine and Thymine always join together A T Cytosine and Guanine always join together C G

24. Watson & Crick proposed… DNA had specific pairing between the nitrogen bases:DNA had specific pairing between the nitrogen bases: ADENINE – THYMINE CYTOSINE - GUANINE DNA was made of 2 long stands of nucleotides arranged in a specific way called the “Complementary Rule”DNA was made of 2 long stands of nucleotides arranged in a specific way called the “Complementary Rule”

25. DNA Double Helix P P P O O O 1 2 3 4 5 5 3 3 5 P P P O O O 1 2 3 4 5 5 3 5 3 G C TA

26. DNA by the numbers Each cell has about 2 m 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. DNA has a diameter of only 0.000000002 m. The earth is 150 billion m or 93 million miles from the sun.

27. Genetic Diversity… Different arrangements of NUCLEOTIDES in a nucleic acid (DNA) provides the key to DIVERSITY among living organisms.Different arrangements of NUCLEOTIDES in a nucleic acid (DNA) provides the key to DIVERSITY among living organisms.

28. The Code of Life… The “code” of the chromosome is the SPECIFIC ORDER that bases occur.The “code” of the chromosome is the SPECIFIC ORDER that bases occur. A T C G T A T G C G G…