PowerPoint Notes On Chapter 7-1 - Meiosis

2y ago
29 Views
2 Downloads
515.57 KB
5 Pages
Last View : 2m ago
Last Download : 2m ago
Upload by : Samir Mcswain
Transcription

Copy into Note Packet and Return to TeacherPowerPoint Notes on Chapter 7-1 - MeiosisSection 1: MeiosisObjectivesSummarize the events that occur during meiosis.Relate crossing-over, independent assortment, and random fertilization to geneticvariation.Compare spermatogenesis and oogenesis.Formation of Haploid CellsMeiosis is a form of cell division that halves the number of chromosomes when formingspecialized reproductive cells, such as gametes or spores.Meiosis involves two divisions of the nucleus—meiosis I and meiosis II.Before meiosis begins, the DNA in the original cell is replicated. Thus, meiosis startswith homologous chromosomes.The eight stages of meiosis are:oProphase I: The nuclear envelope breaks down. Homologous chromosomespair. Crossing-over occurs when portions of a chromatid on one homologouschromosome are broken and exchanged with the corresponding chromatidportions of the other homologous chromosome.oMetaphase I: The pairs of homologous chromosomes are moved by the spindleto the equator of the cell.oAnaphase I: The chromosomes of each pair are pulled to opposite poles of thecell by the spindle fibers.oTelophase I: Individual chromosomes gather at each of the poles. In mostorganisms, cytokinesis occurs.oProphase II: A new spindle forms around the chromosomes.oMetaphase II: The chromosomes line up along the equator and are attached attheir centromeres to spindle fibers.oAnaphase II: The centromeres divide, and the chromatids (now calledchromosomes) move to opposite poles of the cell.oTelophase II: A nuclear envelope forms around each set of chromosomes, andthe cell undergoes cytokinesis.

Stages of MeiosisComparing Meiosis and Mitosis (Video clip)Both start off with the same number of chromosomes and these chromosomes arepaired. Each pair contains 2 homologous chromosomes.DifferencesMeiosisMitosisHomologous chromosomes pairChromosomes line up singly; NoChromosomesup to form tetrads; Crossing-overcrossing over occurs.Line Upoccurs; Resulting chromosomesare different from parent cell.Separation ofChromosomesResult of DivisionChromatids are still attached toHomologous chromosomes linedeach other as the homologousup singly and the chromatidschromosomes separate.separate.Each cell produced has only oneEach cell produced has one copychromosome out of each pair ofof both of the homologoushomologous chromosomes.chromosomes. Mitosis stopshere.The daughter cells divide again.This time the chromatidsSecond divisionseparate. There are now fourdaughter cells and each cell hasonly one copy of every pair ofhomologous chromosomes.No second division.

Comparing the Results of Meiosis and Mitosis (Video clip)End ResultsMeiosisMitosisNumber of CellsProduced4 cells2 cellsChromosome NumberHalf as many chromosomes haploidSame number of chromosomes diploidGenetic Comparisonto Parent CellGenetically differentGenetically identicalMeiosis and Genetic VariationMeiosis is an important process that allows for the rapid generation of new geneticcombinations.Three mechanisms make key contributions to this genetic variation:1. independent assortment2. crossing-over3. random fertilizationIndependent AssortmentThe random distribution of homologous chromosomes during meiosis is called independentassortment.

Crossing-Over and Random FertilizationThe DNA exchange that occurs during crossing-over adds even more recombination tothe independent assortment of chromosomes that occurs later in meiosis.Thus, the number of genetic combinations that can occur among gametes is practicallyunlimited.Furthermore, the zygote that forms a new individual is created by the random joining oftwo gametes.Crossing-Over of ChromosomesImportance of Genetic VariationMeiosis and the joining of gametes are essential to evolution. No genetic processgenerates variation more quickly.The pace of evolution is sped up by genetic recombination. The combination of genesfrom two organisms results in a third type, not identical to either parent.Meiosis in MalesThe process by which sperm are produced in male animals is called spermatogenesis.Spermatogenesis occurs in the testes (male reproductive organs), and produces malegametes called sperm.Formation of Sperm (Video clip)During sperm formation, the cytoplasm is divided equally after the 1st meiotic division.The cytoplasm is divided equally again after the 2nd meiotic division.Thus, 4 sperm result from each cell that begins meiosis.Meiosis in FemalesThe process by which gametes are produced in female animals is called oogenesis.

Oogenesis occurs in the ovaries (female reproductive organs) and produces femalegametes called ova.Formation of the Egg Cell (Video clip)During egg formation, the cytoplasm is divided unequally after both meiotic divisions.One large cell and 3 smaller cells result.The 3 smaller cells die.Thus only 1 egg or ovum results from each cell that begins meiosis.Meiosis in Male and Female Animals

Meiosis is a form of cell division that halves the number of chromosomes when forming specialized reproductive cells, such as gametes or spores. Meiosis involves two divisions of the nucleus—meiosis I and meiosis II. Before meiosis begins, the DNA in the original cell is replicated. Thus, meiosis starts with homologous chromosomes.

Related Documents:

Part One: Heir of Ash Chapter 1 Chapter 2 Chapter 3 Chapter 4 Chapter 5 Chapter 6 Chapter 7 Chapter 8 Chapter 9 Chapter 10 Chapter 11 Chapter 12 Chapter 13 Chapter 14 Chapter 15 Chapter 16 Chapter 17 Chapter 18 Chapter 19 Chapter 20 Chapter 21 Chapter 22 Chapter 23 Chapter 24 Chapter 25 Chapter 26 Chapter 27 Chapter 28 Chapter 29 Chapter 30 .

TO KILL A MOCKINGBIRD. Contents Dedication Epigraph Part One Chapter 1 Chapter 2 Chapter 3 Chapter 4 Chapter 5 Chapter 6 Chapter 7 Chapter 8 Chapter 9 Chapter 10 Chapter 11 Part Two Chapter 12 Chapter 13 Chapter 14 Chapter 15 Chapter 16 Chapter 17 Chapter 18. Chapter 19 Chapter 20 Chapter 21 Chapter 22 Chapter 23 Chapter 24 Chapter 25 Chapter 26

DEDICATION PART ONE Chapter 1 Chapter 2 Chapter 3 Chapter 4 Chapter 5 Chapter 6 Chapter 7 Chapter 8 Chapter 9 Chapter 10 Chapter 11 PART TWO Chapter 12 Chapter 13 Chapter 14 Chapter 15 Chapter 16 Chapter 17 Chapter 18 Chapter 19 Chapter 20 Chapter 21 Chapter 22 Chapter 23 .

About the husband’s secret. Dedication Epigraph Pandora Monday Chapter One Chapter Two Chapter Three Chapter Four Chapter Five Tuesday Chapter Six Chapter Seven. Chapter Eight Chapter Nine Chapter Ten Chapter Eleven Chapter Twelve Chapter Thirteen Chapter Fourteen Chapter Fifteen Chapter Sixteen Chapter Seventeen Chapter Eighteen

18.4 35 18.5 35 I Solutions to Applying the Concepts Questions II Answers to End-of-chapter Conceptual Questions Chapter 1 37 Chapter 2 38 Chapter 3 39 Chapter 4 40 Chapter 5 43 Chapter 6 45 Chapter 7 46 Chapter 8 47 Chapter 9 50 Chapter 10 52 Chapter 11 55 Chapter 12 56 Chapter 13 57 Chapter 14 61 Chapter 15 62 Chapter 16 63 Chapter 17 65 .

HUNTER. Special thanks to Kate Cary. Contents Cover Title Page Prologue Chapter 1 Chapter 2 Chapter 3 Chapter 4 Chapter 5 Chapter 6 Chapter 7 Chapter 8 Chapter 9 Chapter 10 Chapter 11 Chapter 12 Chapter 13 Chapter 14 Chapter 15 Chapter 16 Chapter 17 Chapter

Chapter 3 Chapter 4 Chapter 5 Chapter 6 Chapter 7 Chapter 8 Chapter 9 Chapter 10 Chapter 11 Chapter 12 Chapter 13 Chapter 14 Chapter 15 Chapter 16 Chapter 17 Chapter 18 Chapter 19 Chapter 20 . Within was a room as familiar to her as her home back in Oparium. A large desk was situated i

The Hunger Games Book 2 Suzanne Collins Table of Contents PART 1 – THE SPARK Chapter 1 Chapter 2 Chapter 3 Chapter 4 Chapter 5 Chapter 6 Chapter 7 Chapter 8. Chapter 9 PART 2 – THE QUELL Chapter 10 Chapter 11 Chapter 12 Chapter 13 Chapter 14 Chapter 15 Chapter 16 Chapter 17 Chapt