Chapter 8 - Cellular Reproduction
Chapter 8 - Cellular Reproduction Biology 110 002
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This 3 page Class Notes was uploaded by Kathleen Maris on Sunday October 11, 2015. The Class Notes belongs to Biology 110 002 at University of South Carolina - Columbia taught by Dr. Dhameja in Fall 2015. Since its upload, it has received 213 views. For similar materials see General Biology in Science at University of South Carolina - Columbia.
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Date Created: 10/11/15
Chapter 8 Cellular Reproduction 0 The continuity of life is based on the reproduction of cells or cell division 0 In unicellular organisms division of one cell reproduces the entire organism 0 All of the DNA in a cell constitutes the cell s genome 0 Cell division is an integral part of the cell cycle the life of a cell from formation to its own division 0 DNA molecules in a cell are packaged into chromosomes I Every eukaryotic species has a characteristic number of chromosomes in each cell nucleus 0 The eukaryotic cell cycle consists of two phases I Interphase wherein the cell grows and copies its chromosomes in preparation for cell division It s about 90 of the cell cycle 0 G1 phase first gap 0 S phase synthesis 0 G2 phase second gap I Mitotic M phase wherein the cell divides 0 MitosisMeiosis division of nucleus 0 Cytokinesis division of cytoplasm happens during late telophase Eli2E 213311 E 31 mirem WEE n REIT1 InnPE O Mitosis is the process of cell division that produces daughter cells with identical genetic information I Cells that go through mitosis are called somatic cells I Somatic cells make up the entire body except testes and ovaries I The mitotic spindle is an apparatus of microtubules that controls chromosome movement during mitosis I Mitosis has five phases 0 Prophase in which the assembly of spindle microtubules begins in the centrosome the microtubules organizing center 0 The centrosome replicates forming two centrosomes that migrate to opposite ends of the cell as spindle microtubules grow out of them 0 Prometaphase in which some spindle microtubules attach to the chromosomes and begin to move them 0 Metaphase in which the chromosomes are lined up at the metaphase plate the midway point between the spindle s two poles Metaphase is the longest phase 0 Anaphase in which sister chromatids separate and move toward opposite ends of the cell Anaphase is the shortest phase 0 Microtubules from opposite poles overlap and push against each other elongating the cell Telophase in which genetically identical daughter nuclei form at opposite ends of the cell I At the end of telophase cytokinesis the separation of the cell membrane occurs by a process known as cleavage forming a cleavage furrow Meiosis is the process of cell division that produces gametes sperm or egg in reproductive organs testes and ovaries of male and female respectively I Meiosis occurs in cells called seX cells or germ cells I Meiosis yields nonidentical daughter cells that have only one set of chromosomes half as many as the parent cell I Meiosis has two separation phases meiosis I and meiosis II which creates four haploid cells holding 23 chromosomes all unique 0 In meiosis I homologous chromosomes separate 0 In meiosis II sister chromatids separate I Fertilization is the union of gametes 0 The fertilized egg is called a zygote and has one set of chromosomes from each parent 0 The zygote produces somatic cells by mitosis and develops into an adult Sexual reproduction is responsible for most genetic variations which occur by three mechanisms I Independent assortment of chromosomes in which homologous pairs of chromosomes orient randomly at metaphase I of meiosis 0 Each pair of chromosomes sorts maternal and paternal homologues into daughter cells independently of the other pairs 0 The number of combinations possible when chromosomes assort themselves independently into gametes is 2 where n is the haploid number For humans n23 there are more than 8 million possible combinations of chromosomes Crossing over in which homologous portions of two nonsister chromatids trade places 0 Crossing over begins very early in prophase I as homologous chromosomes pair up gene by gene 0 It combines DNA from two parents into a single chromosome Random fertilization in which any sperm can fuse with any egg 0 A karyotype is the ordered display of the pairs of chromosomes in a cell The two chromosomes in each pair are called homologous chromosomes 0 The only pair of chromosomes that is not homologous is the seX chromosome pair in males 0 The seX chromosomes are called X and Y Human females have two X s and human males have an X and a Y The 22 pairs of chromosomes that do not determine seX are called autosomes Each pair of homologous chromosomes includes one chromosome from each parent Chromosomes in a homologous pair are the same length and carry genes controlling the same inherited characters 0 Cancer cells are the result of a loss of cell cycle controls 0 Normal cells are converted to cancerous cells by a process called transformation 0 Cancer cells form tumors masses of abnormal cells within normal tissue If abnormal cells remain at the original site the lump is called a benign tumor Malignant tumors invade surrounding tissues and can metastasize eXporting cancer cells to other parts of the body where they may form secondary tumors
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