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Chapter 12.1 DNA

Chapter 12.1 DNA. DNA’s Responsibilities. Genes carry information from one generation to the next Genes determine the heritable characteristics of organisms Genes can be replicated or copied exactly. DNA’s Components. DNA is a nucleic acid It has monomers called  nucleotides

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Chapter 12.1 DNA

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  1. Chapter 12.1DNA

  2. DNA’s Responsibilities • Genes carry information from one generation to the next • Genes determine the heritable characteristics of organisms • Genes can be replicated or copied exactly

  3. DNA’s Components • DNA is a nucleic acid • It has monomers called  nucleotides • Each nucleotide is composed of three basic parts:  5 carbon sugar – deoxyribose • A phosphate group • A nitrogenous base

  4. Nitrogenous Bases • There are four nitrogenous bases categorized into two groups Purines: (two rings) • Adenine (A) • Guanine (G) Pyrimidines: (one ring) • Cytosine (C) • Thymine (T)

  5. DNA’s Structure • DNA can be considered to be like a ladder The sugar and phosphate groups make up the backbone of the molecule, or the sides of the ladder • They alternate along the sides The nitrogenous bases stick out of the sides of the sugar • They make up the rungs of the ladder

  6. Erwin Chargaff • Realized the number of A’s equals the number of T’s and that the number of G’s equals the number of C’s • Base pairing rule A = TG = C PurinesPyrimidines

  7. Rosalind Franklin Used x-ray diffraction to gather information about DNA structure • Revealed that DNA is in helix form (coil or twisted ladder)

  8. Watson and Crick • Made 1st 3-D model of a DNA molecule • Used the work of Chargaff and Franklin to create this model • DNA structure is called a double helix, in which two strands are wound around each other The two strands are connected by hydrogen bonds

  9. DNA and Chromosomes Chromosomes are tightly wound up DNA strands • Increased organization allows for the tremendous length of DNA to fit into the nucleus of the cell

  10. Chromosome Structure • DNA is tightly wound around proteins called histones 8 histones + DNA = nucleosome • These form chromatin • Chromatin tightly wound up makes a chromosome • http://www.youtube.com/watch?v=yqESR7E4b_8&feature=related

  11. Prokaryotic Chromosomes • Prokaryotic chromosomes are located floating in the cytoplasm of the cell (not in the nucleus) They are circular in shape (not “X shape” like in eukaryotes)

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