1. UNDERSTANDING HEREDITY PROTEIN SYNTHESIS 1

2. Genes & Proteins Genes - sequences of nucleotide bases Genes code for proteins Proteins - amino acids linked together by peptide bonds 20 different amino acids exist 2

3. 3 Genes & Proteins Amino acid chains are called polypeptides So: Protein = polypeptide Ribbon Structure of Mouse Cholera Antibody

4. 4 Starting with DNA DNA - found inside the nucleus Proteins are made in the cytoplasm of cells by organelles called ribosomes Ribosomes may be free in the cytoplasm or attached to the surface of rough ER

5. 5 Starting with DNA DNA ‘s code must be copied and taken to the cytoplasm In the cytoplasm, this code must be read so amino acids can be assembled to make proteins This process is called protein synthesis

6. RNA 6

7. 7 Roles of RNA & DNA DNA = COOKBOOK RNA = KITCHEN CREW

8. 8 Roles of RNA & DNA RNA is a disposable copy of a portion of DNARNA is a disposable copy of a portion of DNA It is used to construct a proteinIt is used to construct a protein Comparison of RNA and DNAComparison of RNA and DNA RNADNA SugarRiboseDeoxyribose Nitrogen BasesC G A U(racil)C G A T StructureSingle HelixDouble Helix

9. 9. Three Types of RNA Messenger RNA - mRNA Ribosomal RNA - rRNA Transfer RNA - tRNA

10. 10 Messenger RNA (recipe) Long chain of nucleotides Made in the nucleus Transcribes DNA & leaves through nuclear pores Carries information for a specific protein to ribosome

11. 11 Ribosomal RNA (head chef) rRNA is a single strand 100 to 3000 nucleotides long Globular in shape Made in the nucleolus of a cell Reads mRNA and assembles proteins

12. 12 Transfer RNA (kitchen staff) Clover-leaf shape Single stranded molecule with attachment site at one end for an amino acid Found out in the cytoplasm Brings amino acid to ribosome

13. 13

14. 14 The Genetic Code Codon - a set of three RNA bases Codon - designates a specific amino acid An amino acid may have more than one codon and there are 64 codons

15. Transcription and Translation 15

16. 16 Protein Synthesis The production or synthesis of polypeptide chains (proteins) Two phases: Transcription & Translation mRNA must be processed before it leaves the nucleus of eukaryotic cells

17. 17 Transcription The process of mRNA copying the sequence of one strand of DNA During transcription, RNA polymerase binds to DNA and separates the DNA strands RNA Polymerase then uses one strand of DNA as a template to assemble nucleotides into RNA

18. 18 What would be the mRNA strand for the following DNA sequence? DNA 5’-GCGTATGAA-3’ mRNA 3’-CGCAUACUU-5’

19. 19 STEPS OF TRANSCRIPTON: 1.RNA polymerase binds to DNA just before code for protein begins 2.Nucleotide bases are added to make strand of mRNA 3.RNA polymerase detaches from DNA and mRNA 4.Enzymes proofread the mRNA sequence before it leaves nucleus

20. 20 mRNA Transcript mRNA leaves the nucleus through its pores and goes to the ribosomes

21. 21Translation Translation = the process of decoding the mRNA into a polypeptide chain Ribosomes read mRNA three nucleotide bases or 1 codon at a time

22. STEPS OF TRANSLATION: 1.mRNA transcript start codon AUG attaches to the ribosome 2.Amino acids are brought to the ribosome by tRNA 3.tRNA plugs into the mRNA with an anticodon 4.The amino acids are attached like beads on a string 5.tRNA is released to cytoplasm; mRNA is disassembled 6.Stop codon tells ribosome to release protein 22

23. 23 Summary of Protein Synthesis TranscriptionTranslation DNA mRNA tRNA amino acid protein code copy anticode assemble product

24. Mutations are Mistakes Mistakes in gene code cause mistakes in the protein These mistakes are called mutations In protein synthesis mutations involving one base are called point mutations Some mutations may do nothing to the final protein others may do serious damage 24