DNA-The code of life

1. DNA-The code of life Why don’t we all look alike?

2. CODON • 3 LETTER GROUPING OF NITROGEN BASE PAIRS • AGC • ATT

3. WARM-UP #7

4. Why do we Study DNA? • Disease • Better vegetable, fruit, and animals. • Crime • History of life

5. DNA Facts • One chromosome has 50 - 250 million base pairs. • DNA is found in the mitochondria. • mDNA is only found in the egg. Sperm has no mitochondria so mDNA is passed to offspring from the mother. • One sequence of DNA is a genome or gene. • Unwind all our DNA, it will stretch from the moon and back 6000X.

6. http://public.ornl.gov/hgmis/gallery/

8. Gene: segment of DNA on your chromosomes that determines your traits. • Trait: characteristics about you. It can be a part or a behavior. You inherited your traits from your parents. • What is the human genome?

9. Genetic material of cells… • GENES – units of genetic material that CODES FOR A SPECIFIC TRAIT • Called NUCLEIC ACIDS • DNA is made up of repeating monomers called NUCLEOTIDES

10. DNA(Deoxyribonucleic Acid)

11. A HISTORY OF DNA • Discovery 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)

12. Discovery of DNA Invented X-ray diffraction photography. Photo used to determine the shape of DNA is spiral. Rosalind Franklin -

13. DISCOVERY OF DNA James Watson and Francis Crick used the information from Franklin and other scientists to build a 3-D model of DNA. Won the Nobel Piece Prize in Chemistry in 1961.

15. Watson & Crick proposed… • 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”

16. DNA DNA stands for – Deoxyribonucleic acid Functions of DNA: 1. Carries the codes to make proteins. • Pass on genes/traits from parent to child

17. STRUCTURE OF DNA These three parts form the basic unit of DNA called the NUCLEOTIDE. phosphate Nitrogen base Can be A, T, C or G Sugar (deoxyribose)

18. STRUCTURE OF DNA Side Pieces(The Rope Part) Are alternating units of a 5 carbon sugar and a phosphate group. These go down both sides of the molecule phosphate Sugar (called deoxyribose)

19. STRUCTURE OF DNA Nitrogen Bases (Steps of the ladder) - • Adenine - A • Thymine – T • Cytocine – C • Guanine - G The bases are connected to the sugar only !!!!!

20. Phosphate Group O O=P-O O 5 CH2 O N Nitrogenous base (A, G, C, or T) C1 C4 Sugar (deoxyribose) C3 C2 DNA Nucleotide

21. phosphate adenine sugar thymine cytocine guanine

22. How are the nucleotides held together? • Nucleotides are held together by covalent bonds between the sugar of one nucleotide and the phosphate of the next.

23. DNA

24. “Rungs of ladder” Nitrogenous Base (A,T,G or C) “Legs of ladder” Phosphate & Sugar Backbone DNA Double Helix

25. A or G T or C Nitrogenous Bases • A + T = 2 bonds; C + G = 3 bonds • PURINES 1. Adenine (A) 2. Guanine (G) • PYRIMIDINES 3. Thymine (T) URACIL for RNA 4. Cytosine (C)

26. H-bonds G C A T BASE-PAIRINGS 2 Bonds 3 bonds

27. STRUCTURE OF DNA One complete turn of the double helix is 10 base pairs or 10 steps on the ladder

28. 5 O 3 3 O P P 5 5 C O G 1 3 2 4 4 2 1 3 5 O P P T A 3 5 O O 5 P P 3 DNA Double Helix

29. C T A G Chargaff’s Rule • Adeninemust pair with Thymine • Guanine must pair with Cytosine • Their amounts in a given DNA molecule will be about the same.

30. Chargaff’s Rule • Chargaff discovered that the percentage of A and T were equal. The same for C and G. This observation became Chargaff’s rule. This is always the same no matter what organisms.

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

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

34. DNA is wrapped tightly around histones and coiled tightly to form chromosomes See p. 297

35. How does DNA copy itself? Purpose:DNA copies itself to ensure that each new cell that is produced in gets the correct number of chromosomes and receives an EXACT copy of the DNA molecule. Replication must occur before cell division.

36. This is called DNA REPLICATION. • The DNA molecule serves as its own pattern or templateso as an exact copy can be made.

37. Watson and Crick • The model that Watson and Crick where the nitrogen bases pair suggested a mechanism for DNA to replicate.

38. Messelson and Stahl • They proved that DNA is semiconservative by attaching radioactive material to DNA. As the cell divided, they observed the new DNA in each cell and saw that it contained half of the old. • Semiconservative: contains half of the old strand when DNA is replicated.

39. STEPS OF DNA REPLICATION 1. Helicase begin to unzip the double helix at many different places. The hydrogen bonds between the bases are broken. Occurs in two different directions. 2. Free floating in the cytoplasm nucleotides pair with the bases on the template. DNA polyermasebonds together the nucleotides. Small segments are bonded together.

40. Two identical strands of DNA result. The DNA will twist back together. DNA is called SEMICONSERVATIVE because it uses an old strand to make a new one. • This results in 2 new identical DNA molecules.

41. DNA Replication Video http://www.youtube.com/watch?v=zdDkiRw1PdU&feature=player_embedded

42. DNA Replication Fork Point where DNA is split apart to replicate. Forms a Y!

43. Role of Enzymes • 1. Helicase unzips the two DNA strands. • 2. DNA polymerase is the enzyme that joins individual nucleotides to produce a new strand of DNA. Proofreads DNA when finished!

44. DNA Replication in Prokaryotic Cells • 1. Proteins binds to starting point. • 2. Starts at a single point and proceeds in both directions.

45. Eukaryotic Replication • Since eukaryotic cells are so much bigger, the replication will start at dozens to hundreds of different places on the DNA.

46. DNA REPLICATION What if there is a mistake? There is always a chance that the wrong nucleotide bonds to another. HOWEVER, DNA polymerase is responsible for “reading” the bases and recognizing and replacing damaged or wrong nucleotides. This PROOFREADING allows for only one (1) error in ONE BILLION nucleotides.

47. DNA Fingerprinting • When DNA is found at a crime, the DNA is replicated many times to make enough to test. Once they have fingerprinted it, they can compare to find suspect. • Video • http://www.bing.com/videos/search?q=dna+crime+scene&view=detail&mid=684167203C024AD0C797684167203C024AD0C797&first=21&FORM=LKVR22&adlt=strict

48. DNA Fingerprinting

49. Speed of DNA Replication • In the human cell, 50 nucleotides can be added every second. It would that several days for replication to occur if the DNA did not start at several spots on the DNA so that it is occurring in many places on the DNA strand.

50. Transciption – Making of RNA • Transcription – process of copying DNA to produce a complimentary strand of RNA. Transcription is making RNA from DNA • Purpose = to make RNA that is complimentary to the DNA