Scarlet Encina Spring2013 BSC 2011 Cumulative Final Dixon 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 collected o The dependent variable is the event studied and expected to change whenever the independent Recitation Extras Experimental test VS Observational test Variables o Dependent variable the output or effect o Independent the inputs or cause Experiments test a hypothesis and variables are manipulated variable is altered Ex Gender affects height Gender independent variable Height dependent Citing a scientific paper o 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 2 159 169 Lecture 2 Cell Life Cycle Cells grow synthesis DNA and divide in a cycle with distinct phases o The cell cycle consists of both DNA replication and cell division Functions of cell division o Reproduction growth and repair 1 Scarlet Encina Spring2013 o Results in genetically identical daughter cells DNA is organized into chromosomes o Composed of DNA and protein histones all tightly wrapped up in one package o Duplicated chromatids are connected by a centromere G1 phase S phase G2 phase M Mitotic phase Mitosis Interphase DNA replicates Growth 2 Cell division Cytokinesis The separation of copied chromosomes into separate cells The G2 checkpoint ensures that DNA replication in S phase has been completed successfully The metaphase checkpoint ensures that all of the chromosomes are attached to the mitotic spindle by a kinetochore Cell life cycle G 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 replicate 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 cycle Cell cycle checkpoints normally ensure that DNA replication and mitosis occur only when conditions are favorable and the process is working correctly 2 Scarlet Encina Spring2013 These check points molecular signals are important because unregulated cell division can lead to cancer o 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 o Prometaphase o Metaphase Meet o Anaphase Apart 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 Spindle fibers from each centriole attach to each sister chromatid at the kinetochore The centrioles complete their migration to the poles The chromosomes meet in the middle of the cell the equator 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 chromosomes o Telophase Tear The chromosomes decondense The nuclear envelope forms Lecture 3 Plant growth division Meristems are sites of cell division in plants Cleavage furrow appears cytokinesis divides the cytoplasm creating two daughter cells 3 Scarlet Encina Spring2013 o 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 DNA o Separate coding region for regulatory gene o 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 it o 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 translation o Chromatin modification DNA packaging o Transcription RNA modification RNA transport o Translation o Post translation protein modification degradation transport Modification of histone structure can affect transcription o Histones package and order the DNA into nucleosomes o Unacetylated histones DNA methylation packages DNA to BLOCK transcription from occurring o Acetylated histones acetylation unravels histones to START transcription Enhancers and transcription factors can affect transcription o Can result in cell specific transcription 4 Scarlet Encina Spring2013 Lecture 5 Cell Determination VS Cell Differentiation Cell Determination No phenotype change Developmental pathway is set Cell Differentiation Become phenotypically different Cell differentiation occurs during early development because of different concentrations of cytoplasmic determinants o Developmental pathway is set early Lecture 6 Development Fertilization and Cleavage Development consists of fertilization cleavage gastrulation and organogenesis Polyspermy is blocked by 2 mechanisms in sea urchins o 1st Fast block Response to acrosomal reaction Fast but temporary o 2nd Slow block Response to corticol reaction and Ca the formation of the fertilization envelope Slow but permanent Blocking multiple fertilizations is important because only one sperm can fuse with an egg at a time in order to fertilize successfully Cleavage is cell division without growth Cleavage has different patterns in different organisms Protostomes Invertebrates mollusks annelids arthopods Vertebrates echinoderms chordates
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