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Cell Cycle

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University of British Columbia
BIOL 121
Robert Adamson

Chapter 11-Cell Cycle -multicellular eukaryotes start as single-celled embryo and grow thru cell division Chromosomes-carry hereditary material/instructions for building + operating cell -made up of single DNA double helix wrapped around proteins Gamete-haploid reproductive cell, fuse w/ another haploid cell to form zygote (eg. egg and sperm cells) Somatic cells-body cells (cell in multicellular org. that isn’t sperm/egg) Meiosis/reduction division-hereditary material in parent cell reduced by half, occurs in animals just to form gametes Mitosis-daughter cells genetically identical to parent cell (hereditary material is constant), followed by.. Cytokinesis (“cell movement”)-cytoplasm divides into the 2 daughter cells In multicellular eukaryotes, Mitosis + Cytokinesis responsible for… 1. Growth-all identical cells that make up body are from one fertilized egg (result of sperm+egg) 2. Wound repair-cells that repair skin generated by M + C 3. Reproduction-asexual reproduction (offspring genetically identical to parent) eg. yeast cells 11.1 Mitosis and the Cell Cycle Gene-segment of DNA that codes for certain protein or RNA in cell Mitotic (M)-dividing phase (M + C) where copied chrom. given to daughter cells, no replication Interphase (between phase)-nondividing (cells spend most time here, chro. replication) Synthesis (S) phase-DNA synthesized, chromosomes replicated Cell cycle-starts with formation of eukaryotic cell to time it undergoes cell division M phase (6-8 hrs) -> G₁ (7-9) -> S phase (6-8) -> G₂ (4-5) -> M phase, etc. Gap phases-no DNA synthesis, organelles replicate, more cytoplasm made (prep parent cell for division-make sure big enough) 11.2 How Does Mitosis Take Place? Histones-proteins associated with DNA Chromatin-DNA + protein (i.e. histones) complex that compose eukaryotic chromosomes Chromatid-each of the DNA copies in a replicated chromosome, each has 1 long DNA double helix Sister Chromatids-chromatids from the same chromosome, joined along length and centromere 1. Interphase a) G₁ (parent cell with unreplicated chromosomes) b) S Phase (chromosomes in parent cell replicate to form sister chromatids) c) G₂ (at this point, each chromosome consists of 2 sister chromatids) 1. Mitosis a) Chromatin condense, more compact b) Sisters separate + form independent chromosomes Centrioles-pair forms centrosome-the microtubule organizing center in animals IPPMAT 1. Prophase -chromosomes condense (now visible in microscope) -mitotic spindles form (made of microtubules, produces mechanical forces), move toward poles 2. Prometaphase -nuclear envelope breaks down, spindle fibers from each mitotic spindle attach to kinetochores -centrosomes keep moving t
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