1 DNA And RNA The illustration is a ‘model’ of the double helix forming part of a DNA molecule (Slide 14)

DNA stands for deoxyribose nucleic acid RNA stands for ribonucleic acid 2 This chemical substance is present in the nucleus of all cells in all living organisms DNA controls all the chemical changes which take place in cells The kind of cell which is formed, (muscle, blood, nerve etc) is controlled by DNA The kind of organism which is produced (buttercup, giraffe, herring, human etc) is controlled by DNA

DNA is a very large molecule made up of a long chain of sub-units DNA molecule 3 DNA is a very large molecule made up of a long chain of sub-units The sub-units are called nucleotides Each nucleotide is made up of a sugar called deoxyribose a phosphate group -PO4 and an organic base

Ribose is a sugar, like glucose, but with only five Ribose & deoxyribose 4 Ribose is a sugar, like glucose, but with only five carbon atoms in its molecule Deoxyribose is almost the same but lacks one oxygen atom Both molecules may be represented by the symbol

Takes the place of thymine in RNA The bases The most common organic bases are 5 Adenine (A) Thymine (T) Cytosine (C) Guanine (G) Uracil: Takes the place of thymine in RNA (U)

Combine to form a nucleotide Nucleotides 6 The deoxyribose, the phosphate and one of the bases Combine to form a nucleotide adenine deoxyribose PO4 It is the phosphate group which gives DNA its acidic properties

RNA Ribonucleic Acid (RNA) Sugar + Phosphate Backbone Differs from DNA Single Stranded Ribose Sugar Base Pairs A-U, G-C Are there T’s in RNA? A, U no T’s in RNA RNA assists DNA in manufacturing needed proteins

Questions Name one difference between DNA and RNA. DNA – Double Helix, RNA – Single Stranded DNA --- A-T, RNA ---A-U DNA ---Deoxyribose Sugar, RNA---Ribose What is a similarity of DNA and RNA? G binds with C in both DNA and RNA Both have sugar and phosphate backbone