1. 1 Unit 4 The Code of Life

2. 2 Topic 3 Gene Expression

3. Human Genome Complete set of all human DNA –Specific to each individual person – i.e. Your DNA is not exactly the same as anyone else’s – Unless…..? (Almost) Every cell contains all ~6 billion base pair of DNA! –2 sets of ~3 billion – Why 2 sets? Hmmmm Segmented into 23 pairs of chromosomes 3

4. 4 Genes and Traits Genes – section of DNA that codes for a protein –~21,000 proteins (only!) Genotype - Letters in your DNA Phenotype - physical trait or characteristics Central Dogma of Biology: DNA RNA Protein OBJ 9 genotypephenotype

5. Written Language is a code! ABCDEFGHIJKLMNOPQRSTUVWXYZ –26 characters –Specific sequences are required to communicate. –RACECAR has meaning but….. – RRAACCE does not DNA has a 4 base code…. –ATCG –Specific sequences are required to produce specific proteins 5

6. Gene Expression - Overview Process of using the information in DNA to make proteins Steps: –Transcription – copies DNA code to RNA code –Translation – converts RNA code to Amino acid sequence Both steps involve.. –RNA –Enzymes 6 OBJ 9

7. 7 Gene Expression in Eukaryotes Cell structures involved… Nucleus Nuclear pore Ribosome (Rough ER) Building blocks needed…. Free RNA nucleotides Free Amino Acids

8. 8 DNA vs. RNA OBJ 10 Ribonucleic Acid Ribose sugar Single stranded Contains Uracil (not Thiamine) Uracil base pairs with Adenine 3 types… mRNA – messenger RNA rRNA – ribosomal RNA tRNA – transfer RNA

9. 9 OBJ 11 Codon Set of 3 RNA nucleotide bases that corresponds to a single amino acid “words” of the genetic code

10. 10 OBJ 11 Genetic Code Codons and corresponding Amino Acids Redundant code

11. 11 Practice reading the genetic code What is the sequence of amino acids made from the following RNA strand? AUGAAGUUUCUCUAG Met-Lys-Phe-Leu

12. Transcription – A closer look The Transfer of genetic information from coding regions of DNA (genes) to messenger RNA. –Promoter – section of DNA that indicates a start of a gene, RNA polymerase binding site –Terminator – section of DNA that indicates the end of a gene 12 OBJ 12

13. RNA Polymerase Enzyme that reads the DNA template and base pairs the correct RNA nucleotide 13 OBJ 12

14. TranscriptionTranscription – 3 steps 14 OBJ 12

15. 15 OBJ 13 Messenger RNA processing DNA genes contain coding and noncoding sections. Exon – coding region Intron – noncoding region mRNA splicing – the removal of the introns and connection of exons

16. 16 OBJ 13

17. 17 RNA Types mRNArRNAtRNA OBJ 14

18. Messenger RNA (mRNA) Single stranded Formed during transcription Copied Gene sequence 18 Obj 14

19. Ribosomal RNA (rRNA) Ribosome composed of… –Protein –RNA 2 Sub units –Large –Small 19 Obj 14

20. Transfer RNA (tRNA) Carry Amino Acids Anticodon –Base pairs to codons 20 OBJ 14

21. 21 An aminoacyl-tRNA synthetase joins a specific amino acid to a tRNA

22. 22 OBJ 15 Translation – A Closer Look Ribosome Provides the binding sites for mRNA and tRNA to base pair (Codon to anti-codon) Forms peptide bond between amino acids Moves mRNA through one codon at a time.

23. 23 The anatomy of a functioning ribosome OBJ 15

24. 24 Transcription – Step by step OBJ 15

25. 25 Translation – Stop codons OBJ 15

26. 26 Detailed Overview – Transcription, RNA processing and Translation OBJ 15 Also, called: Protein Synthesis

27. 27 thesunwashotbuttheoldmandidnotgethishat the sun was hot but the ole man did not get his hat the sun was hot but the old man did not get his cat the sun was hot but the old ma. did not get his hat thd esu nwa sho tbu tth eol dma ndi dno tge thi sha t OBJ 15

28. 28 Mutations Mutation - any change in the DNA sequence Point mutation –Silent –Missense –Nonsense OBJ 16

29. 29 Mutations Frameshift –Insertion –Deletion OBJ 16

30. 30 What causes mutations? Mutation Rate –~1.1 x 10 -8 per base per generation DNA Polymerase mistakes (rare) Mutagens –UV light –Radiation –Chemicals OBJ 16

31. 31 The molecular basis of sickle-cell disease: a point mutation OBJ 16

32. 32 Topic 4 Control of gene expression

33. 33 Cell differentiation Selective gene expression –Turning genes on and off What gene is needed in red blood cells, but not in the pancreas?? OBJ 17

34. 34 Gene Regulation - Example The Lac Operon Lactase expression regulation in bacteria

35. 35 OBJ 18 DNA Coiling Histones – proteins that DNA wraps around Chromatin – partially coiled DNA, most common state of DNA Chromosome – completely wound form of DNA, only present during cell replication

36. 36 Chromosome Supercoils Coils Nucleosome Histones DNA double helix OBJ 18 DNA Coiling

37. Gene Regulation 37 Genes are regulated by the level of DNA coiling Coiling is controlled by… DNA methylation Histone modifications Obj 18

38. Epigenetics 38 Study of heritable components other than DNA Some DNA methylation passes from parent to offspring