3.3 7.1 Dna Structure

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3.3 7.1 Dna Structure

  1. 1. Topics 3.3 & 7.1Nucleic Acids<br />IB Biology<br />
  2. 2. Where can you find it?<br />Inside the cell<br />- nucleus, chloroplasts and mitochondria<br />Chromosomes are made of DNA<br />
  3. 3. Nucleic Acids<br />Polymers: <br />DNA (deoxyribonucleic acid) <br />RNA (ribonucleic acid)<br />Units: nucleotides<br />Nucleotide: sugar + nitrogenous base + phosphate<br />
  4. 4. Parts of a Nucleotide<br />Phosphate<br />Sugar: Ribose or Deoxyribose (both pentoses)<br />Nitrogenous Bases: <br /> - Purines (double rings): Adenine + Guanine<br /> - Pyrimidines (single ring): Cytosine, Thymine, Uracil (RNA only)<br />
  5. 5. Structure of DNA<br /><ul><li>Discovery of Double Helix: 1962
  6. 6. James Watson, Francis Crick and Maurice Wilkins received a NOBEL PRIZE
  7. 7. Watson, Crick and Wilkins used unpublished data from Rosalind Franklin’s research obtained without her knowledge and used without her consent.</li></ul> - She was misrepresented and unrecognized <br /> - She died of cancer in 1958<br /><ul><li>We know now: DNA is a double helix made of... </li></ul> - 4 nucleotides - A, T, G, C  <br /> - in 2 polynucleotide strands    <br />- strands run antiparallel - [5&apos;-----3&apos;] - held together via weak H-Bonds & complimentary base pairing (A-T and C-G)<br />
  8. 8. DNA is double-stranded, withcomplementary base pairing<br />
  9. 9. Observe <br />- hydrogen bonds<br />- complementary base pairing :<br />A – T<br />C – G <br />- covalent bonds between 2 nucleotides (formed through condensation)<br />
  10. 10. Counting Carbons...<br />Anti-parallel strands<br />One side 5’  3’<br />Other side 3’  5’<br />
  11. 11. DNA Structure<br />In eukaryotes it is always associated with proteins<br />NUCLEOSOMES = DNA wrapped around 8 histones (proteins)<br />Help compact DNA <br />Help control DNA transcription<br />
  12. 12. Single copy x Highly repetitive sequences<br />Much of DNA in eukaryotes = repetitive base sequences, which are not translated (satellite DNA) = 5-300 bases / repeated as many as 10,000x<br />5-45% of DNA = function not clear<br />Single copy/unique genes = actually code for something (small proportion)<br />
  13. 13. DNA’s job<br />Stores information<br />It has the code for all 20 amino acids<br />Mutation: changes in the base sequence  primary structure of a protein is altered (changing its shape)<br />Can be harmful, neutral or beneficial <br />Important: create variation – basis of natural selection<br />
  14. 14. RNA<br />Discovered after DNA<br />Single strand shorter than DNA<br />Contains Uracil instead of Thymine<br />Sugar = ribose (DNA contains deoxyribose)<br />DNA: nucleus, mitochondria, chloroplasts<br />RNA: nucleus, cytoplasm, part of ribosomes<br />Types:<br /><ul><li>RNAm: messenger blueprint for protein
  15. 15. RNAr: ribosomal  makes up ribosomes
  16. 16. RNAt: transfer  delivers the proper amino acid to the ribosome</li></li></ul><li>

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