1. The Code of Life: Topic 4 Regulation of gene expression

2. What determines your phenotype?

3. Selective gene expression Can you think of a gene that is needed in red blood cells but not in the pancreas? And vice versa? Regulation of gene expression starts with cell differentiation during in-utero development. Neuron (nerve cell) muscle cells liver cells

4. Chromosome Supercoils Coils Nucleosome Histones DNA double helix DNA Coiling Affects Gene Expression DNA is negatively charged (phosphate groups) Histone proteins are positively charged This makes the DNA wrap around groups (8-9) of histones Each wrapped group is called a nucleosome The string then coils due to further charged-region interactions

5. Levels of chromatin packing

6. Chromatin modifications This can be modified by two processes: Methylation: addition of methyl functional groups to histone proteins. Acetylation: addition of acetyl functional groups to histone proteins. DNA coiling: making it difficult for enzymes to reach some portions of the DNA for transcription and keeps other portions exposed. Acetylation

7. Epigenetics The study of how environmental factors can change gene expression without a change in DNA by resulting in methylation. Examples: –Diet (during development and beyond) –Stress –Hormones –Chemicals –Inheritance of methylation patterns

8. Extra slides

9. Regulation of gene expression Regulation occurs at many stages: –Chromatin coiling and modification –Transcription –Processing –Translation

10. Regulation of gene expression Transcription

11. Alternative RNA Splicing

12. Gene DNA Exon 1Exon 2 Exon 3 Intron Transcription RNA processing Translation Domain 2 Domain 3 Domain 1 Polypeptide