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Notes on Mitosis/Meiosis/Genetics

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York University
BIOL 1500

Week 5 Sections 8186 89817 275 101 105Cell Cycle Mitosis and Meiosis and DNA ReplicationExplain why cell division is essential for prokaryotic and eukaryotic lifeProkaryotic cells divide by binary fission asexual because genetically identical offspring inherit their DNA from a single parent eukaryotic cells divide by mitosis and cytokinesis Cell division is an integral part of the growth of multicellular organisms and it is also the basis of reproduction Cell division enables sexually reproducing organisms to develop from a single cell the fertilized egg or zygote into an adult or organism Example would be humans who began with a single fertilized egg cell in our mothers body After an organism is grown cell division functions as a renewal and repair replacing cells that die from normal wear and tear or accidentsCompare the parentoffspring relationship in asexual and sexual reproductionAsexual reproduction the creation of genetically identical offspring by a single parent without the participation of a sperm and an egg The lone parent and each of its offspring have the same genes Ex Sea stars and PlantsSexual reproduction Requires fertilization of an egg and sperm For an egg and sperm to be produced you need mitosis and meiosis A gamete is a fusion of an egg and sperm and contains chromosomes which contain a unique combination of genes Offspring produced by sexual reproduction generally is more related to their parents then unrelated individuals of the same species but are not identical to their parents or each other It can produce great variation among offspringIdentify and describe a chromosome in G1 G2 and M phasesDescribe the stages of the eukaryotic cell cycle1Interphase G1 Phase S Phase and G2 Phase Most of cell cycle spent hereG1 Phase Cellular contents excluding the chromosomes are duplicatedS Phase Each of the 46 Chromosomes are duplicated by the cell each chromosome now consists of two sister chromatidsG2 Phase The cell double checks for the duplicated chromosome for error making any needed repairs2Mitotic Phase M Phase Divided into 2 stages of Mitosis and CytokinesisMitosis The nucleus and its contents specifically the duplicated chromosomes divide and are evenly distributed forming two daughter nucleiCytokinesis Begins before mitosis ends and the cytoplasm is divided into twoThe combination of mitosis and cytokinesis produces two genetically identical daughter cells each with a single nucleus surrounding cytoplasm with organelles and a plasma membrane Cycle is then repeatedDistinguish between homologous chromosomes and sister chromatidsHomologous chromosomes are like the chromosomes an individual inherits from their parents Like you receive an X from your mother and a Y from your father if you are a boy The X and Y are homologous chromosomes because they code genes for similar traits though they code for different traits Of your 46 chromosomes they make 23 pairseach of those pairs are homologs or homologous chromosomes Sister chromatids are the chromosomes when a cell undergoes DNA replication A chromosome will replicate and one sister chromatid will go to each daughter cell resulting from the division The DNA in sister chromatids are identical assuming no crossing over and synapsis occursRelate cell density anchorage and growth factors to cell divisionGrowth FactorsA growth factor is a protein made by certain body cells that stimulate other cells to divide Researchers have identified 50 different growth factors that can trigger cell division Different cell types respond specifically to certain growth factors or a combination of growth factorsEx Protein called vascular endothelial growth factor VEGF which stimulates the growth of new blood vessels during fetal development and injuryCell Density Crowded cells stop dividingEx Animal cells growing on a dish may multiply to cover the dish and stop dividing when there is no space and they are touching each other They divide until the vacancy is filledCounter example Cancer cells do not exhibit density dependent inhibition Cancer cells continue to divide even at higher densities piling up on one another
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