1. Chapter 12 – DNA and Proteins DNA Structure: DNA is made of many smaller subunits called nucleotides.

2. A nucleotide has 3 parts: 1.A sugar (a 5 Carbon deoxyribose) 2.A Phosphate group 3.A nitrogenous base - 4 types of these a Adenine (A) Thymine (T) Cytosine (C) Guanine (G) Always pair up Adenine and Guanine are purines (bigger) Cytosine and Thymine are pyrimidines (smaller)

3. These subunits are arranged in a twisted ladder called a double helix. If you untwisted the ladder, it would look like this: (your teacher will draw this below)

5. The sequence (or order) of the bases in all organisms’ DNA is what makes them different from each other.

6. Protein Synthesis Remember! - Proteins have specific shapes for specific functions - Proteins are made from long chains of 20 types of amino acids DNA tells our cells how to put proteins together. - Different proteins exist because amino acids are assembled in different sequences.

7. Steps of protein synthesis: 1.Transcription – In the nucleus, the DNA code is “copied” onto a molecule of messenger RNA (mRNA) by matching up base pairs. RNA contains uracil (U) instead of thymine(T). After transcription, the mRNA leaves the nucleus and moves to the ribosome.

8. 2. Translation – The ribosome reads the mRNA in 3-base sequences called codons. Specific amino acids are added to a growing protein chain. They are matched up with an anticodon found on a transfer RNA (tRNA) molecule.

9. End Result: Different polypeptide or protein chains can be made from different amino acid sequences. These proteins will have different functions!