Scarlet Encina Spring2013BSC 2011 Cumulative Final (Dixon)Recitation Extras: • Experimental test VS Observational test• Variableso Dependent variable – the output or effecto Independent – the inputs or cause• Experiments test a hypothesis and variables are manipulated o The dependent variable is changed in response to changes made in the independent variables• Observational tests do not manipulate variable, data is simply observed and collectedo The dependent variable is the event studied and expected to change whenever the independent variable is altered Ex: “Gender affects height”• Gender – independent variable• Height – dependent• Citing a scientific papero Citations within the article:(Last name, year) (Smith, 2013)o Citations after the article: Last, First name. (year) Title of Article. Title of Journal. Volume (issue): page # Smith, John. (2013). Study of Biology. Molecular Cell. 217(2): 159- 169Lecture 2: Cell Life Cycle• Cells grow, synthesis DNA, and divide in a cycle with distinct phaseso The cell cycle consists of both DNA replication and cell division• Functions of cell division:1Scarlet Encina Spring2013o Reproduction, growth, and repairo Results in genetically identical daughter cells• DNA is organized into chromosomes o Composed of DNA and protein (histones) all tightly wrapped up in one packageo Duplicated chromatids are connected by a centromere • Cell life cycle:Interphase MitosisG1 phase S phase G2 phase M (Mitotic) phaseG indicates “gap” but think of “growth 1” – cell gathers what it needs for cell replication in S*The G1 checkpoint ensures that the cell is large enough to divide, and that enough nutrients are available to support the resulting daughter cells.*Cells that do not pass this check point don’t replicateDNA replicates“Growth 2”* The G2 checkpoint ensures that DNA replication in S phase has been completed successfullyCell division - Cytokinesis The separation of copied chromosomes into separate cells* The metaphase checkpoint ensures that all of the chromosomes are attached to the mitotic spindle by a kinetochore** Regulation of the Cell Cycle • The cell cycle is controlled by external stimuli (chemical messages) that both trigger and coordinate key events in the cell cycle2Scarlet Encina Spring2013• Cell-cycle checkpoints normally ensure that DNA replication and mitosis occur only when conditions are favorable and the process is working correctly. • These check points/ molecular signals are important because unregulated cell division can lead to cancero Mutations in genes that encode cell-cycle proteins can lead to unregulated growth, resulting in tumor formation and ultimately invasion of cancerous cells to other organs.• Mitosis:o Prophase – “Prepare” The chromosomes condense and become visible The centrioles form and move toward opposite ends of the cell ("the poles") The nuclear membrane dissolves The mitotic spindle forms (from the centrioles in animal cells)o Prometaphase Spindle fibers from each centriole attach to each sister chromatid at the kinetochoreo Metaphase – “Meet” The centrioles complete their migration to the poles The chromosomes meet in the middle of the cell ("the equator")o Anaphase – “Apart” Spindles attached to kinetochores begin to shorten• In other words, spindles short from the tips This exerts a force on the sister chromatids that pulls them apart. Spindle fibers continue to shorten, pulling chromatids to opposite poles. This ensures that each daughter cell gets identical sets of chromosomeso Telophase – “Tear” The chromosomes decondense The nuclear envelope forms Cleavage furrow appears, cytokinesis divides the cytoplasm, creating two daughter cells3Scarlet Encina Spring2013Lecture 3: Plant growth/ division• Meristems are sites of cell division in plantso Found in tips of branches and roots• Development occurs after cell division o Plants grow larger via cell division and cell elongation. Plant growth is facilitated by meristem tissue because it is the primary site of cell division (mitosis) in the plant. Plants develop new organs (stems, leaves, flowers, roots) via cell division and cell differentiation. Lecture 4: Gene Expression • Every cell in your body has the same genes (genotype)o HOWEVER, not all genes are activated – “expressed” through phenotype• Gene expression refers to the transcription and translation of genes • Control of transcription occurs through the binding of activators or repressors to special sites on the DNAo Separate coding region for regulatory geneo Regulatory gene codes for repressor that binds to operator region at start of coding region• ‘Signal molecule’ interacts with repressor to switch on or off*o Signal is co-repressor in an anabolic system - final product turns off gene Gene is expressed continuously – until the repressor stops ito Signal is inducer in a catabolic gene - substrate turns on gene Gene is not expressed unless the inducer is present• Gene expression in eukaryotes can be controlled at multiple stages during transcription and translationo Chromatin modification - (DNA packaging)o Transcription, RNA modification, RNA transporto Translationo Post translation - protein modification, degradation, transport• Modification of histone structure can affect transcriptiono Histones package and order the DNA into nucleosomes o Unacetylated histones (DNA methylation) – packages DNA to BLOCK transcription from occurring4Scarlet Encina Spring2013o Acetylated histones – acetylation unravels histones to START transcription • Enhancers and transcription factors can affect transcriptiono Can result in cell specific transcriptionLecture 5: Cell Determination VS Cell DifferentiationCell Determination Cell Differentiation- No phenotype change- Developmental pathway is set- Become phenotypically different • Cell differentiation occurs during early development because of different concentrations of cytoplasmic determinantso Developmental pathway is set earlyLecture 6: Development – Fertilization and Cleavage• Development consists of fertilization, cleavage,
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