DNA + RNA

• Chromosomes are made of DNA and protein.
• Chromosomes contain all of our genetic information
• chromosomes occur in pairs in all somatic cells ( diploid)
• Chromosomes are found in the nucleus of all cells
• DNA = Deoxyribonucleic Acid
• DNA consists of two strands of nucleotides twisted together in a spiral shape called the double helix.
• • Each nucleotide is made of:
  • A five carbon sugar – deoxyribose 
  • A phosphate group
  • A nitrogen base:
  • Purine: Adenine (A) and Guanine (G)
  • Pyrimidine: Cytosine (C) and Thymine (T)
• • The phosphate and sugar groups form the sides of the DNA strand.
• • The nucleotides are joined together with a bond between the phosphate of one nucleotide and a sugar of the next.
• The two strands are held together by Hydrogen Bonds.
• • The two nucleotide strands are anti parallel to each other. 
• The two strands are bonded together by hydrogen bonds between complementary base pairs.
• Adenine bonds to Thymine via 2 hydrogen bonds
• Cytosine bonds to Guanine via 3 hydrogen bonds
• A purine base always bonds to a pyrimidine base.
• James Watson and Frances Crick are credited with the discovery of the 3D structure of DNA
• • Purine: Adenine (A) and Guanine (G)
• • Pyrimidine: Cytosine (C) and Thymine (T)