Independent Variable o Experimental something you have control over it can be changed manipulated it is usually what you think will affect the dependent variable Example girl or boy o Observational sometimes you cannot manipulate it because it is already fixed but can measure how it affects the dependent variable affects the dependent variable by natural processes the cause Dependent variable the same in both experimental and observational the response that is measured something that is changed affected by the independent variable the effect Example reading comprehension Cite a scientific journal o In text Last Name Publication Date Smith 1982 o End of paper citation Last Name First Name Initial Publication Year The title of the Article Title of the Journal followed by the volume number page numbers Smith J 1982 The life history of the blue footed booby Science 57 213 221 Know that cells grow synthesize DNA and divide in a cycle with distinct phases o Cell cycle G1 S G2 Mitosis Cytokinesis o A cell grows in G1 G2 phases synthesizes DNA where chromosomes are duplicated in the S phase and separates in the Cytokinesis phase o The mitotic phase is the shortest part of the cell cycle Understand that the cell cycle is controlled by molecules present in the cytoplasm that regulate movement of the cycle past checkpoints o G1 checkpoint triggers the cell to duplicate DNA go into S Phase either pass it and synthesize or they get thrown out and don t go through mitosis o G2 checkpoint is after the last growth phase to see if the cell should pass through to divide in mitosis o M checkpoint is to see if cell is ready to completely divide in cytokinesis after mitosis o Cycli n Cdk are two different molecules that when together result in MPF which is a composite molecule Cyclin and Cdk are good examples of negative feedback when Cdk and Cyclin get together and make MPF is triggers the cell to go into Mitosis mitosis breaks down Cyclin which therefore stops the process because no MPF available if Cyclin can t get with Cdk to form MPF the thing that causes the process also ends it to control mitosis so it doesn t happen indefinitely Understand that meristems are sites of cell division and that development occurs after cell division o Meristems part of the plants that produce new cells produce new structures the meristems make the plant have indeterminate growth elongates the plant like a stem cell o Meristems Divide Make new cells Elongate o Main meristem repressing activities of other meristems if you were to cut off the main meristems then it would allow the other meristems to grow towards the outwards direction not up Control of transcription occurs through the binding of activators or repressors to special sites on the DNA o Trp operon is turned on RNA can bind to promoter and transcribe the genes of that operon but can be turned off by the trp repressor which binds to promoter prevents transcription of the genes o If trp is removed along with repressor then theres nothing to prevent transcription so trp A E will continuously transcribe o Transcription is deactivated when tryptophan is there or when lactose is absent o Signal molecule interacts with the repressor to switch it on or off Know that gene expression in eukaryotes can be controlled at multiple stages during transcription and translation o Gene expression subset of genes expressed in the cells of each type is unique allowing these cells to carry out their specific function o The differences between cell types therefore are due not due to different genes being present but due to differential genes being expressed activated o Control of gene expression in eukaryotes can occur at Chromatin modification DNA packaging in the chromosome Transcription RNA modification RNA transport Translation Post translation protein modification degradation transport Know that modification of histone structure can affect transcription o DNA is wrapped around histones with histone tails Methylation methyl groups being attached to DNA which prevents transcription therefore deactivating it Acetylation acetyl groups attached to histone tails which repel each other creating more room exposing more DNA increase gene expression Know that enhancers and transcription factors can affect transcription o Activator proteins bind to distal control elements grouped as an enhancer in the DNA a DNA bending protein brings the bound activators closer to the promoter the activators bind to certain mediator proteins and general transcription factors helping them form an active transcription initiator complex on promoter o Specific transcription factors determine which genes are expressed same genes present in the liver and lens cells however each gene has different activators to express each one Cell differentiation occurs during early development because of different concentrations of cytoplasmic determinants o Determinant pattern for that cell and all succeeding ones have already been set maternal substances In the egg that influence the course of early development already present in mothers egg before fertilization o Differentiation become phenotypically different more specialized in structure and function o Hox genes switch boards that control what set of genes become what in the cell which genes are turned on in which cells o The two different determinants were already present in the mother after being fertilized mitosis the egg split and based on the determinants it went on to differentiate into two different kinds of cells that will have different structure function orange vs green Understand that polyspermy is blocked by 2 mechanisms in sea urchins and why blocking multiple fertilizations is important o The sperm hits the jelly coat of the egg releases enzymes onto the surface of the egg that eats through the coat receptor proteins are waiting on the egg for these enzymes acrosomal processes make sure its th appropriate sperm for the species like a lock and key sperm enters the egg but don t want polyspermy so changes egg surface becomes depolarized results in fast block polyspermy no other sperm can penetrate occurs within 1 3 seconds of contact and lasts 1 minute cell membranes of the egg and sperm fuse sperm enters the egg cortical reaction forms fertilization envelope and cell membrane pulls away from vitelline layer fertilization envelope hardens and acts as a slow block to polyspermy permanent block occurs 20 sec 1 min after contact sperm egg nuclei fuse
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