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    Dna Dna Presentation Transcript

    • DNA Structure & Function
    • Key terms
      • Genome = complete set of sequences in the genetic material of an org.
      • Nucleic acids = Macromolecules (large RMM).
      • Chromosomes = Discrete unit of the genome carrying many genes . NA and protein.
      • Gene = Segment of DNA specifying production of a polypeptide chain . It codes for a RNA protein.
      • Genotypic = Replication . Store &transmit info.
      • Phenotypic = Gene expression. Control devlp of phenotype.
      • Evolutionary = Mutation. Changes produce variations.
      • Fx…..preserving, copying and transmitting information.
      • Chromosomes composed of 2 macmol.
      • i. Protein.
      • ii. Nucleic acids DNA(d) and RNA(s)
    • Structure of nucleotides..
      • A ) 5 carbon pentose sugar ;
      • RNA = Ribose, DNA = Deoxyribose.
      • b) A nitrogen containing base;
      • 2 Purines (A,G) 2 Pyrimidines (C,T/U)
      • RNA = CGA U , DNA = CGA T
      • c) A phosphate group
    • Pentose sugars
    • Structure of nucleotides
    • Watson and Crick’s model
      • double helix
      • sugar-phosphate backbone = sugar is deoxyribose
      • 4 types of nucleotide base : A, C, G, T
      • : 2 complementary strands where A = T, C = G in anti parallel fashion
        • "complementary“ = fitting together of 2 molecules with hydrogen bonds
    • Phosphodiester bonds..
      • A dinucleotide is formed when a condensation reaction occurs between the phosphate group of one nucleotide and pentose of another forming a phosphodiester bridge linking the 2 nucleotides together.
    • More nucleotides can be added, building up a long polynucleotide chain.
      • The stability of the double helix is due to the large number of covalent, H+ and hydrophobic bonds.
    • Double Helix.. Uprights = Sugar phosphate bond, Rungs = Bases (A+T/G+C) 2 strands running in opposite direction (5’ – 3’) <>
    • Genetic code
      • These bases always pair up in the same way.
      • A single strand of DNA is made of letters: ATGCTCGAATAAATG
      • The letters make words: ATG CTC GAA TAA ATG TGA ATT TGA
      • The words make sentences: <ATG CTC GAA TAA> <ATG TGA ATT TGA>
      • These &quot;sentences&quot; are called genes
    • Genetic code
      • The instructions in a gene that tell the cell how to make a specific protein. A, T, G, and C.
      • 3 letter word = codon = Triplet code.
      • Fx of codon = tell the cell how to make proteins
      • Start and stop codon.
    • Genetic code contd..
      • Inside the nucleus, the DNA message is copied onto RNA. to transmit the message or genetic code.
      • It has 4 subunits A, T, G, C and are arranged in triplet codes. Eg ATTGCCTAG read from left to right ATT/GCC/TAG. Each triplet code specifies different amino acids.
      • Eg. ATT = amino acid “X”
      • GCC = amino acid “Y”
      • TAG = amino acid “Z”
      • This piece of genetic code will instruct the cell to make a protein in which X,Y and Z are joined together in that order.