Fig. 18-3b-2 (b) Tryptophan present, repressor active, operon off Tryptophan (corepressor) No RNA made Active repressor mRNA Protein DNA

Fig. 18-4b (b) Lactose present, repressor inactive, operon on mRNA Protein DNA mRNA 5 Inactive repressor Allolactose (inducer) 5 3 RNA polymerase Permease Transacetylase lac operon  -Galactosidase lacY lacZlacAlac I

Fig DNA Signal Gene NUCLEUS Chromatin modification Chromatin Gene available for transcription Exon Intron Tail RNA Cap RNA processing Primary transcript mRNA in nucleus Transport to cytoplasm mRNA in cytoplasm Translation CYTOPLASM Degradation of mRNA Protein processing Polypeptide Active protein Cellular function Transport to cellular destination Degradation of protein Transcription Levels of gene regulation in eukaryotes - Eukaryotes can control the availability of DNA for expression by altering the extent of DNA packing

Fig a DNA double helix (2 nm in diameter) Nucleosome (10 nm in diameter) Histones Histone tail H1 DNA, the double helixHistones Nucleosomes, or “beads on a string” (10-nm fiber)

Figure 18.7 Amino acids available for chemical modification Histone tails DNA double helix Nucleosome (end view) (a) Histone tails protrude outward from a nucleosome Unacetylated histones Acetylated histones (b) Acetylation of histone tails promotes loose chromatin structure that permits transcription

Figure 7-80 Molecular Biology of the Cell (© Garland Science 2008)

Fig X chromosomes Early embryo: Allele for orange fur Allele for black fur Cell division and X chromosome inactivation Two cell populations in adult cat: Active X Inactive X Black furOrange fur

Fig Histone tails DNA double helix (a) Histone tails protrude outward from a nucleosome Acetylated histones Amino acids available for chemical modification (b) Acetylation of histone tails promotes loose chromatin structure that permits transcription Unacetylated histones Fig Normal Igf2 allele is expressed Paternal chromosome Maternal chromosome Normal Igf2 allele is not expressed Mutant Igf2 allele inherited from mother (a) Homozygote Wild-type mouse (normal size) Mutant Igf2 allele inherited from father Normal size mouse (wild type) Dwarf mouse (mutant) Normal Igf2 allele is expressed Mutant Igf2 allele is expressed Mutant Igf2 allele is not expressed Normal Igf2 allele is not expressed (b) Heterozygotes

Figure 7-82 Molecular Biology of the Cell (© Garland Science 2008)

Fig DNA Signal Gene NUCLEUS Chromatin modification Chromatin Gene available for transcription Exon Intron Tail RNA Cap RNA processing Primary transcript mRNA in nucleus Transport to cytoplasm mRNA in cytoplasm Translation CYTOPLASM Degradation of mRNA Protein processing Polypeptide Active protein Cellular function Transport to cellular destination Degradation of protein Transcription Levels of gene regulation in eukaryotes -Alternative splicing can be generated

Fig or RNA splicing mRNA Primary RNA transcript Troponin T gene Exons DNA Alternative splicing

The DSCAM gene (Drosophila): ~38,000 possible splice variants

Fig DNA Signal Gene NUCLEUS Chromatin modification Chromatin Gene available for transcription Exon Intron Tail RNA Cap RNA processing Primary transcript mRNA in nucleus Transport to cytoplasm mRNA in cytoplasm Translation CYTOPLASM Degradation of mRNA Protein processing Polypeptide Active protein Cellular function Transport to cellular destination Degradation of protein Transcription Levels of gene regulation in eukaryotes - Proteins can be selectively degraded

Fig Proteasome and ubiquitin to be recycled Proteasome Protein fragments (peptides) Protein entering a proteasome Ubiquitinated protein Protein to be degraded Ubiquitin Ubiquitin ligase

Fig b Cyclin is degraded Cdk MPF Cdk M S G1G1 G 2 checkpoint Degraded cyclin Cyclin (b) Molecular mechanisms that help regulate the cell cycle G2G2 Cyclin accumulation

Fig. 12-6d MetaphaseAnaphase Telophase and Cytokinesis Cleavage furrow Nucleolus forming Metaphase plate Centrosome at one spindle pole Spindle Daughter chromosomes Nuclear envelope forming

Fig DNA Signal Gene NUCLEUS Chromatin modification Chromatin Gene available for transcription Exon Intron Tail RNA Cap RNA processing Primary transcript mRNA in nucleus Transport to cytoplasm mRNA in cytoplasm Translation CYTOPLASM Degradation of mRNA Protein processing Polypeptide Active protein Cellular function Transport to cellular destination Degradation of protein Transcription Levels of gene regulation in eukaryotes Small, non-coding RNAs can affect gene regulation at multiple levels

Fig DNA Signal Gene NUCLEUS Chromatin modification Chromatin Gene available for transcription Exon Intron Tail RNA Cap RNA processing Primary transcript mRNA in nucleus Transport to cytoplasm mRNA in cytoplasm Translation CYTOPLASM Degradation of mRNA Protein processing Polypeptide Active protein Cellular function Transport to cellular destination Degradation of protein Transcription Levels of gene regulation in eukaryotes Small, non-coding RNAs can affect gene regulation at multiple levels

Nematodes with a GFP transgene Treated with GFP dsRNA

dsRNA can reduce gene expression for generations

Fig miRNA- protein complex (a) Primary miRNA transcript Translation blocked Hydrogen bond (b) Generation and function of miRNAs Hairpin miRNA Dicer 3 mRNA degraded 5