Biology Unit 1

Structure of DNA
1. DNA molecule
  1. Base pairs (A,T,G,C)
    1. Determines genotype
    2. Held together by weak hydrogen bonds
  2. Deoxyribose Sugar
    1. Joined by a strong chemical bond
  3. Phosphate
  4. Genetic information stored in the DNA
  5. Double stranded helix
    1. 3' end and 5' end
      1. starts with deoxyribose
      2. Finishes with a phosphate
Organisation of DNA
1. Prokaryotes
  1. Circular chromosomal DNA & plasmids
    1. Also found in yeast calls
  2. Bacteria
2. Eukaryotes
  1. nuclei that contain linear chromosomes
    1. tightly coiled around proteins
  2. Mitochondria & chloroplast contain circular chromosomes
  3. Animals
  4. Fungi
  5. Green plant
Replication of DNA
1. 1. DNA is replicated by DNA Polymerase
  1. A primer is needed to start replication
    1. Short sequence of nucleotides formed at the 3' end of the parent strand
2. 2. DNA is unwound to form 2 template strands
  1. This occurs in several locations on the DNA molecule
3. 3. DNA Polymerase adds complimentary nucleotides to the 3' end
4. 4. DNA Polymerase can only do this in 1 direction
  1. So one strand (leading 3'-5') can be replicated continuously
    1. So the other strand (lagging 5'-3') is replicated in fragments
      1. The fragments are joined together by ligase
5. For all this to happen things need to be present:
  1. a DNA template
  2. free DNA nucleotides
  3. ATP to break H bonds
  4. DNA primer
  5. DNA Polymerase
  6. Ligase
Polymerase Chain Reaction (PCR
1. a technique used for the amplification of DNA in vitro (in the lab)
2. Primers are complimentary to specific target sequences
  1. The sequences are either end of the region to be amplified
3. Heat is used to separate the DNA strands
4. The strands are then cooled to allow the primers to bond

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