The Cell

Multicellular Life

Organismic and Evolutionary Biology

Lecture_14.docx-Lecture 14  Deuterostomia and Echinoderms

Jenny Xiao BILD1 The Cell mexiao@ucsd.edu Week 7 Handout Complete the table. Experiment Discovery Significance Griffith Avery Hersey and Chase Chargaff Franklin Jenny Xiao BILD1 The Cell mexiao@ucsd.edu Week 7 Handout Watson and Crick Meselson and Stahl Please list the step in DNA replication, including any key players. Jenny Xiao BILD1 The Cell mexiao@ucsd.edu Week 7 Handout Name and explain the proofreading/repairing mechanisms during DNA replication.

BILD | 1 | The Cell | homework | Jenny Xiao BILD1 The Cell mexi

2/26/12 13 • Norms of reaction are generally broadest for multifactorial characters – Characters that are affected by many factors – Often polygenic and – Influenced by both genetic and environmental factors © 2011 Pearson Education, Inc. Integrating a Mendelian View of Heredity and Variation • An organism ’ s phenotype – includes its physical appearanc

Chapter_14_Slides.pdf-Norms of reaction are generally broadest

Problem_Set_03_KEY.pdf-Problem Set 3 BILD1 / Spring

Lecture 15 - Regulation of Gene Expression  Bacteria regulate their gene expression in response to environment o E. coli, a bacteria that lives in human colon, can tune its metabolism to the changing environment and food sources  Metabolic Control on Two Levels o Protein Activity  “Feedback Inhibition ”: Adjust activity of metabolic enzymes already present o Protein Levels  Gene Expression : Regulate transcription of genes encoding metabolic enzymes  Operons: The Basic Concept o Bacterial genes are often clustered into regulated operons o Operons contain:  Operator , an “on-off” switch  Turned OFF by repressor  Promoter , to initiate transcription  Cluster of Genes for metabolic enzymes that act at different steps in same pathway  Repressible and Inducible Operons o In a Repressible Operon  Binding of a specific repressor protein to the operator shuts off constitutive transcription  (operon default is ON, until repressor turns it OFF) o In an Inducible Operon  Binding of an inducer to an innately active repressor inactivates the repressor and turns on transcription  (operon default is OFF, until inducer turns it ON) o Helpful way to remember: Repress ible : CAN BE repressed, so must be ON first; Induc ible , CAN BE induced, so must be OFF first  The trp repressible operon o If repressor (Tryptophan) is absent, NEED Tryptophan synthesis enzymes, then repressor is INACTIVE, and operon is ON o If Tryptophan is present, DO NOT NEED Tryptophan synthesis enzymes, then repressor is ACTIVE, so operon is OFF  The lac inducible operon o Need inducer (Allolactose) to take out the repressor (make it inactive), going from OFF to ON  Inducer / Repressor o Repressible Operons usually function in anabolic (synthesis) pathways o Inducible Operons usually function in catabolic (breakdown) pathways  Positive Gene Regulation o Regulation of the lac operon also involves positive control  Because operon is switched on by the stimulatory activator protein  A unique subset of genes is expressed in each cell type  Organisms regulate which genes are expressed at any time  Gene Expression Regulated at Multiple Levels o Transcriptional (Genome) Regulation  Chromatin Modification  Transcription o Post-Transcriptional Regulation  Degradation of mRNA  Translation  Transcription : The key level of regulated gene expression o Each cell transcribes only a fraction of its genes  In eukaryotes, o Genomes are enormous and cells are highly specialized o Genomes must be managed by structural organization o Regions of chromosomes regulated in different states  Unfolded chromatin: each “bead” is a nucleosome , the basic unit of DNA packing o DNA is a negative charge, so nucleosomes are positive o Nucleosomes are the folded loop of proteins/DNA o These loops further loop and loop (like rope) until we end up with the chromatins we recognize  Differential Gene Expression o A unique subset of genes is expressed in each cell type o Organisms regulate which genes are expressed at any time o Two major forms of transcriptional regulation:

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