1. Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings Section 6.1 What Does DNA Look Like?

2. Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings DNA THE STRUCTURE OF DNA –Genetic material that makes up chromosomes –Deoxyribonucleic acid –Made up of nucleotides

3. Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings Nucleotides Subunits of DNA Made up of a sugar, a phosphate, & a base Four bases: guanine (G), cytosine (C), thymine (T), adenine (A) Each base has a different shape

4. Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings Chargaff’s Rule Found amount guanine = amount of cytosine Amount of thymine = amount of adenine. Rosalind Franklin collected the X-ray crystallography images (photographs of DNA molecule) Figure 10.3b (b) Rosalind Franklin

5. Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings James Watson and Francis Crick determined that DNA is a double helix Suggested DNA looked like long twisted ladder Built a model of DNA Watson and Crick’s Discovery of the Double Helix Figure 10.3a (a) James Watson and Francis Crick

6. Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings The model of DNA is like a rope ladder twisted into a spiral or a spiral staircase (this is called a double helix) Figure 10.4 Twist

7. Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings

8. DNA’s Double Structure Twisted ladder, spiral shape or double helix Sides of DNA ladder made of sugar & phosphate Rungs/steps of DNA ladder are the bases – G,C,A,T

9. Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings Base Pairing Adenine always pairs w/Thymine Guanine always pairs w/Cytosine Size & structure of each base allows only these two pairs (bases fit together like a lock & key) This pair arrangement is known as base-pairing rules

10. Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings Complementary The sequence of bases on one strand determines the sequence of bases on other strand. DNA strands are said to be complementary. G C T T G A C C T A

11. Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings DNA molecule splits down middle or unwinds (like a zipper) where bases meet Bases on each side used as pattern for new DNA strand Extra bases float around in cytoplasm Two DNA molecules formed – each has one old & one new strand How are Copies of DNA Made

12. Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings DNA replication –Begins at many sites on a double helix –Proceeds in both directions Figure 10.8 Origin of replication Origin of replication Origin of replication Parental strand Daughter strand Bubble Two daughter DNA molecules

13. Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings DNA copied every time a cell divides Job of unwinding, copying, & re-winding done by proteins When are Copies of DNA Made

14. Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings Chapter 6.2 How DNA Works? DNA  RNA  Protein

15. Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings Unraveling DNA DNA is wound around proteins & coiled into strands Order of bases is code that carries info. Gene is string of bases that give cells info on how to make a specific trait Humans have 30,000 genes

16. Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings DNA holds the directions for making proteins Figure 10.9 DNA Nucleus Transcription RNA Translation Protein Cytoplasm

17. Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings Genes & Proteins DNA code read like a book – from one end to the other Groups of three bases code for a specific amino acid Examples: CCA = proline, AGC = serine

18. Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings Figure 10.10 DNA molecule Translation Protein Gene 1 Gene 2 Gene 3 DNA strand Transcription RNA Codon Amino acid Long string of amino acids forms a protein Proteins act as chemical triggers & messengers for many processes within cells Proteins determine how tall you are, hair color, eye color Genes & Proteins

19. Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings Contains sugar Ribonucleic acid Helps make proteins by changing DNA code into proteins Serves as temporary copy of DNA sequence RNA

20. Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings Making of a Protein STEP 1 Copy one side of DNA segment Mirror-like copy of DNA segment made called messenger RNA (or mRNA) strand of DNA New strand of mRNA

21. Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings STEP 2 Copy transferred to cytoplasm by mRNA nucleus mRNA DNA cytoplasm Making of a Protein

22. Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings STEP 3 Every three bases (called a codon) on mRNA segment codes for one amino acid Making of a Protein

23. Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings STEP 4 mRNA segment fed through protein assembly line called ribosome (3 bases at a time) ribosome translates or reads RNA message Figure 10.16b Next amino acid to be added to protein Growing protein mRNA tRNA Making of a Protein Ribosome

24. Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings STEP 5 tRNA (or transfer RNA) carries amino acids from cytoplasm to ribosome Matches amino acids with codons in mRNA using anticodons Figure 10.15 tRNA Hydrogen bond RNA Anticodon Making of a Protein

25. Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings Protein Amino acid Anticodon mRNA Codons 3 STEP 6 amino acids join together to make protein one protein made for each gene Figure 10.19 mRNA movement Ribosome 1 Making of a Protein tRNA

26. Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings A mutation Mutations – changes in number, type, or order of bases on piece of DNA is called a mutation – mutations happen regularly due to random errors when DNA is copied Figure 10.21 Normal hemoglobin Sickle-cell hemoglobin Glu Val Normal hemoglobin DNA Mutant hemoglobin DNA mRNA

27. Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings Substitution = one base gets switched for another base (most common mutation) 3 Kinds of Mutations Figure 10.22a mRNA Protein MetLysPheGlyAla (a) Base substitution MetLysPheSerAla

28. Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings Deletion = a base is left out Insertion = an extra base is added Figure 10.22b MetLysLeuAlaHis (b) Nucleotide deletion mRNA Protein MetLysPheGlyAla 3 Kinds of Mutations

29. Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings an improved trait no change harmful trait (like sickle cell anemia) Figure 10.22b MetAlaHis MetAla 3 Possible Outcomes of Mutations

30. Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings physical or chemical agent that causes DNA mutation (or damage to DNA) examples: X-ray and UV rays cause damage (can lead to cancer) Mutagens

31. Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings scientists manipulate individual genes in organisms to get a new trait used to create new drugs, food, or fabrics Figure 10.23 Genetic Engineering

32. Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings DNA unique to you! DNA fingerprinting identifies patterns in an individual’s DNA DNA used in crime scenes, identifying family relations, heredity diseases Scientists can clone organisms Clone = new organism with exact copy of another organism’s genes Figure 10.23 Genetic Identification