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Chapter 13: DNA Structure and Replication

Chapter 13: DNA Structure and Replication . Genes Are Made of DNA. Heritable information is carried in units called genes Genes are parts of structures called chromosomes 3. Chromosomes are made of deoxyribonucleic acid ( DNA ) and protein. DNA.

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Chapter 13: DNA Structure and Replication

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  1. Chapter 13: DNA Structure and Replication

  2. Genes Are Made of DNA • Heritable information is carried in units called genes • Genes are parts of structures called chromosomes 3. Chromosomes are made of deoxyribonucleic acid (DNA) and protein

  3. DNA • DNA is made of chains of small subunits called nucleotides

  4. DNA • Each nucleotide has three components: • Phosphate group • Deoxyribose sugar • One of four nitrogen-containing bases • Thymine • Cytosine • Adenine • Guanine

  5. Chargaff’s Rule • In 1940, biochemist E. Chargaff determined that: • In a DNA molecule, amounts of A = T, G = C • “Chargaff’s Rule”

  6. Early DNA Studies • Rosalind Franklin and Maurice Wilkins studied DNA structure using X-ray scattering • From X-ray diffraction patterns they deduced that DNA • Is long and thin • Has a uniform diameter of 2 nanometers • Is helical, and is twisted like a corkscrew • Consists of repeating subunits

  7. DNA Is a Double Helix • James Watson and Francis Crick : • DNA is made of two strands of nucleotides • Deoxyribose and phosphate portions make up the sugar-phosphate backbone

  8. Bases Form Ladder Rungs in DNA • Nitrogen-containing bases protrude inward from sugar-phosphate backbone ghr.nlm.nih.gov

  9. Hydrogen Bonds • Hydrogen bonds hold certain nitrogenous base pairs together • A bonds with T, G bonds with C • Bonding bases called complementary base pairs

  10. DNA is a Double Helix • Ladder-like structure of the two DNA strands are twisted into a double helix

  11. How can a molecule with only 4 simple parts be the carrier of genetic information?

  12. DNA Replication • All cells come from pre-existing cells • Cells reproduce by dividing in half • Each of two daughter cells gets an exact copy of parent cell’s genetic information • Duplication of the parent cell DNA is called replication

  13. DNA Replication • DNA helicases • DNA polymerases

  14. ncbi.nlm.nih.gov

  15. DNA Replication • Base pairingis the foundation of DNA replication

  16. Semiconservative Replication • The two resulting DNA molecules have one old parental strand and one new strand (semiconservative replication)

  17. Replication And Proofreading

  18. Types of Mutations

  19. Point mutation - individual nucleotide in the DNA sequence is changed

  20. Insertion mutation- one or more nucleotide pairs are inserted into the DNA double helix

  21. Deletion mutation • - one or more nucleotide pairs are removed from the double helix

  22. Inversion • - piece of DNA is cut out of a chromosome, turned around, and re-inserted into the gap

  23. Translocation • - chunk of DNA (often very large) is removed from one chromosome and attached to another

  24. The End

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