Chapter 11 - Chapter 11: The Cell Cycle Cell Division...

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Chapter 11: The Cell Cycle Cell Division Creation of new cells by division of pre-existing cells Multicellular individuals start life as singe-celled embryos and grow through a series of cell divisions Chromosomes are the carriers of hereditary material Gametes sperm and eggs Somatic all other cells o Parent cells give rise to daughter cells Meiosis: o Type of cell division in which one diploid parent cell produces four haploid reproductive cells (gametes). o Chromosome pairs synapse and can exchange genes via crossing over Mitosis: o Nuclear division of a eukaryotic cell producing two daughter nuclei that are genetically identical to the parent o Usually accompanied by Cytokinesis: “cell movement” The division of the cytoplasm into the two daughter cells o Mitosis, followed by cytokinesis, supplies the cells required for several key activities in eukaryotes Wound, repair, reproduction, and growth 11.1: Mitosis and the Cell Cycle: o The Cell Cycle: The orderly sequence of events that occurs from the formation of a eukaryotic cell, through the duplication of its chromosomes, to the time it undergoes division of itself Two phases: Interphase o Chromosomes are uncoiled into extremely long, thin structures Mitotic phase, (M-phase) o Chromosomes are condensed into compact structures o During the cycle, two key events: Replication, or copying, of the hereditary material in chromosomes The partitioning of copied chromosomes to the two daughter cells o When Does Chromosome Replication Occur? Interphase: G 1 : First Gap o Occurs after M-phase but before S-phase o Twice as long as G 2 o Where cells perform normal functions S-phase o Where DNA synthesis occurs o Occurs after G 1 G 2 : Second Gap o Where parent cell must grow large enough and synthesize enough organelles that its daughter cells will be normal in size and function o Each chromosome has two chromatids
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11.2: How Does Mitosis Take Place? o Results in the division of chromosomes and the formation of two daughter nuclei o Usually accompanied by cytokinesis o Events in Mitosis: Histones: Globular proteins that is tightly associated with SNA in eukaryotic cells Chromatin: The materical that makes up eukaryotic chromosomes DNA molecule complexed with histone proteins Prior to Mitosis, DNA in each chromosome is copied As Mitosis begins, chromatin condenses to form a much more compact structure Sister chromatids Chromosome Chromosome Centomere Unreplicated Replicated o Chromatid: each of the DNA copies in a replicated chromosome o Centromere: joins the two sister chromatids o Once replication is complete, each chromosome consists of two sister chromatids o Sister chromatids represent exact copies of the same genetic information Each contains a long DNA double helix o Chromosomes are replicated before mitosis begins o At the start of M-phase, chromosomes consist of two sister chromatids that are attached to one
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This note was uploaded on 03/19/2008 for the course BS 111 taught by Professor Patterson during the Fall '05 term at Michigan State University.

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Chapter 11 - Chapter 11: The Cell Cycle Cell Division...

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