1. Topics 3.3 & 7.1Nucleic Acids IB Biology

2. Where can you find it? Inside the cell - nucleus, chloroplasts and mitochondria Chromosomes are made of DNA

3. Nucleic Acids Polymers: DNA (deoxyribonucleic acid) RNA (ribonucleic acid) Units: nucleotides Nucleotide: sugar + nitrogenous base + phosphate

4. Parts of a Nucleotide Phosphate Sugar: Ribose or Deoxyribose (both pentoses) Nitrogenous Bases: - Purines (double rings): Adenine + Guanine - Pyrimidines (single ring): Cytosine, Thymine, Uracil (RNA only)

6. James Watson, Francis Crick and Maurice Wilkins received a NOBEL PRIZE

8. DNA is double-stranded, withcomplementary base pairing

9. Observe - hydrogen bonds - complementary base pairing : A – T C – G - covalent bonds between 2 nucleotides (formed through condensation)

10. Counting Carbons... Anti-parallel strands One side 5’  3’ Other side 3’  5’

11. DNA Structure In eukaryotes it is always associated with proteins NUCLEOSOMES = DNA wrapped around 8 histones (proteins) Help compact DNA Help control DNA transcription

12. Single copy x Highly repetitive sequences Much of DNA in eukaryotes = repetitive base sequences, which are not translated (satellite DNA) = 5-300 bases / repeated as many as 10,000x 5-45% of DNA = function not clear Single copy/unique genes = actually code for something (small proportion)

13. DNA’s job Stores information It has the code for all 20 amino acids Mutation: changes in the base sequence  primary structure of a protein is altered (changing its shape) Can be harmful, neutral or beneficial Important: create variation – basis of natural selection

15. RNAr: ribosomal  makes up ribosomes