The document provides an overview of DNA structure and function. It discusses early experiments that established DNA as the genetic material, including Griffith's experiments showing transformation in bacteria and Avery, Macleod and McCarty's experiments proving that DNA is the transforming principle. It describes Chargaff's rules, Watson and Crick's proposal of the double helix model based on X-ray diffraction data, and semiconservative DNA replication demonstrated by Meselson and Stahl's experiment using nitrogen isotopes.

2. DNA Double Helix, Watson & Crick Nature, 1953 2003 2005 Inactivation of different X genes WHAT IS GENE? Human genome Project

11. Colony morphology Reaction with Antiserum prepared against Type Appearance Size Capsule Virulence Type IIS Type IIIS IIR Rough Small Absent Non-virulent none none IIS Smooth Large Present Virulent Agglutination none IIIR Rough Small Absent Non-virulent none none IIIS Smooth Large Present Virulent none Agglutina

20. Hershey-Chase, 1952 Warring Blender Experiment

27. 6-aminopurine 2-amino-6-oxypurine 4-amino-2-oxypyrimidine 2,4-oxypyrimidine 2,4-oxy-5-pyrimidine Cytosine, thymine, and uracil are single-ring base called Pyrimidines . Adenine and Guanine are double ring base called Purines

32. X-ray diffraction patterns of DNA – Rosalind Franklin and Maurice Wilkins The central cross shaped pattern as indicative of a helical structure. The heavy dark patterns (top and bottom) indicate that the bases are stacked perpendicular to the axis of the molecule.

52. MODELS OF DNA REPLICATION MESELSON AND STAHL EXPT.

55. John Cairns Cairns then isolated the chromosomes by lysing the cells very very gently and placed them on an electron micrograph (EM) grid which he exposed to X-ray film for two months. Grow cells for several generations Small amounts of 3 H thymidine are incorporated into new DNA Grow for brief period of time Add a high concentration of 3 H- thymidine in media with low concentration of 3 H- thymidine Bacterial culture *T *T *T *T Dense label at the replication fork where new DNA is being made *T *T *T *T *T *T *T *T *T *T *T *T *T *T *T *T *T *T *T *T *T *T *T *T *T *T *T All DNA is lightly labeled with radioactivity *T *T *T

59. Origin 5’ 3’ 3’ 5’ U NIDIRECTIONAL R EPLICATION Origin 5’ 3’ 3’ 5’ B IDIRECTIONAL R EPLICATION

63. The origin of replication is located at 14.3 µm from the left end of the chromosome. Four chromosomes are shown at different stage of replication