The illustration is a ‘model’ of the double helix forming part of a DNA molecule (Slide 14)
It is the phosphate group which gives DNA its acidic properties
Structure of DNA 1
What is DNA? • DNA stands for deoxyribose nucleic acid It’s a macromolecule found in the nucleus of all cells in all living organisms • The kind of cell which is formed, (muscle, blood, nerve, etc) is controlled by DNA • The kind of organism which is produced (dog, giraffe, frog, human, etc) is controlled by DNA 2
What is a DNA molecule? • DNA is a very large molecule made up of a long chain of sub-units • The sub-units, or monomers, are called nucleotides • Each nucleotide is made up of: -a sugar called deoxyribose -a phosphate group -PO 4 and -A base (Adenine, Guanine, Cytosine or Thymine) 3
What are the 4 bases? The four bases are: 5 Adenine (A) Thymine (T) Cytosine (C) Guanine (G)
What forms a nucleotide? The deoxyribose, adenine Deoxyribose (sugar) PO 4 the phosphate and one of the 4 bases combine to form a nucleotide: 6 (base)
How do nucleotides form a strand of DNA? • A molecule of human DNA is formed by billions of nucleotides joined together in a long chain sugar-phosphate backbone + bases 7 • In fact, the DNA consists of a double strand of nucleotides PO 4 PO 4 PO 4 PO 4
2-stranded DNA 9 PO 4 PO 4 PO 4 PO 4 PO 4 PO 4 PO 4 PO 4 PO 4 PO 4 PO 4 PO 4 PO 4 PO 4 PO 4 PO 4
How do bases pair together? The bases always pair up in the same way Adenine forms a bond with Thymine and Cytosine bonds with Guanine 10 Adenine Thymine Cytosine Guanine
Bonding 2 11 PO 4 PO 4 PO 4 thymine PO 4 PO 4 PO 4 PO 4 adenine cytosine PO 4 guanine
The paired strands are coiled into a spiral called A DOUBLE HELIX (or TWISTED LADDER) 13 What is the structure of DNA called?
• The DNA of humans is composed of approximately 3 billion base pairs. • If you stretched out the DNA in every cell, it would be almost a meter long! Cool Facts!!!!!