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Nucleic Acids


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Nucleic Acids

  1. 1. Nucleic Acids [revise Higher notes] <ul><li>DNA and RNA are information carrying molecules </li></ul><ul><ul><li>DNA : info storage & transmission </li></ul></ul><ul><ul><li>RNA : protein synthesis </li></ul></ul><ul><li>Simple chemical structure based on a SUGAR PHOSPHATE BACKBONE </li></ul><ul><li>Coding part made of 4 nitrogenous bases which arrange themselves in pairs </li></ul><ul><li>This enables a massive variety and diversity of proteins to be built </li></ul><ul><li>[Diagram of Nas/Nucleotides] </li></ul>
  2. 2. Nucleotides <ul><li>Monomer of nucleic acid </li></ul><ul><li>Consists of 3 main parts : </li></ul><ul><ul><li>a PENTOSE sugar (deoxyribose/ribose) </li></ul></ul><ul><ul><li>a PHOSPHATE group (PO 4 2- ) </li></ul></ul><ul><ul><li>a nitrogenous base ( PURINE or a PYRIMIDINE ) </li></ul></ul>N.B. Base Pairing : A always bonds with T (or U), G with C
  3. 3. Phosphodiester Bond <ul><li>Chains of nucleotides (polynucleotides) formed by DEHYDRATION SYNTHESIS reaction between the phosphate group of one nucleotide and the hydroxyl group on the sugar of another </li></ul><ul><li>This bonding gives polynucleotides a defined polarity reflecting the component nucleotides </li></ul><ul><li>[Diagram of Phosphodiester bond] </li></ul>
  4. 4. Polynucleotides & Nucleic Acid Function <ul><li>Polynucleotide chains provide the structural and functional basis for the encoding and decoding of genetic information. </li></ul><ul><li>The sugar phosphate backbone carries a sequence of bases that makes up the genetic code as a series of triplet codons </li></ul><ul><li>Complementary base pairing holds the key to copying genetic information in the processes of DNA replication and transcription </li></ul><ul><li>The bases fit together A-T(U) and G-C are joined together by HYDROGEN BONDING </li></ul><ul><li>[Base pairing diagram] </li></ul>
  5. 5. DNA <ul><li>A double stranded helix composed of two polynucleotide chains that run in opposite directions (anti-parallel) </li></ul><ul><li>The bases fit across the right-handed helix; one purine pairing with its complementary pyrimidine </li></ul><ul><li>The helix is the only shape that accommodates the purine-pyrimidine base pair and maintains stable hygrogen bonds </li></ul>
  6. 6. RNA <ul><li>3 types of RNA which are SINGLE stranded but can fold to give 3D shapes or conformations: </li></ul><ul><li>mRNA - contains information transcribed from a DNA molecule and transports it to a ribosome </li></ul><ul><li>tRNA - collects amino acids and transports them to a ribosome to be fitted according to the messenger RNA code </li></ul><ul><li>rRNA (ribosomal RNA) - provides a major structural support component of the ribosome </li></ul>
  7. 7. Polymerase enzymes <ul><li>A polymerase is an enzyme whose central function is associated with polymers of nucleic acids such as RNA and DNA </li></ul><ul><li>These are necessary for the following processes: </li></ul>1) DNA REPLICATION: enables a complete copy of the genome to be passed on to each daughter cell during mitosis 2) TRANSCRIPTION OF DNA into RNA: : mechanism by which genes are expressed DNA polymerase
  8. 8. DNA Ligase <ul><li>This enzyme forms phosphodiester bonds which are used to join DNA molecules or fragments together to produce recombinant DNA (recDNA) </li></ul>Both polymerases,ligases and restriction endonucleases (cut DNA) are important components of a genetic engineer’s ‘toolkit’. They are used to manipulate DNA