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Bell Ringer. Cell Division Review. Units 5 & 6. Prokaryotic Cell Division. Prokaryotic Cell Division = Binary Fission After DNA replication occurs, the cytoplasm divides. There is NO nucleus, so mitosis does NOT happen. DNA Replication. Cytokinesis.
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Cell Division Review Units 5 & 6
Prokaryotic Cell Division • Prokaryotic Cell Division = Binary Fission • After DNA replication occurs, the cytoplasm divides. There is NO nucleus, so mitosis does NOT happen.
DNA Replication Cytokinesis This process is called Binary Fission
This is the Cell Cycle M Phase
Eukaryotic Somatic (Body) Cell Division = Mitosis Stages of Cell Cycle • Interphase • G1 = Growth • S = DNA replication • G2 = Prepare for Mitosis • M Phase • Mitosis = Division of Nucleus • Prophase • Metaphase • Anaphase • Telophase • Cytokinesis = Division of Cytoplasm
MITOSIS REPRODUCTION OF BODY CELLS PRODUCES 2 IDENTICAL DIPLOID CELLS
Interphase • Cell Grows & Divides • DNA is Replicated
Prophase • Chromosomesbecome visible • Nuclear Membrane & Nucleolus Disappear EARLY LATE
Metaphase • Spindle Fibers attach to the Centromeres • Chromosomes Line up in the Middle/ Equator
Anaphase • Sister Chromatids are Pulled Apart (separated) to opposite poles of the cell
Telophase • Nuclear Membrane & Nucleolus Reform • Chromosomes Unwind into Chromatin
Cytokinesis • Cytoplasm Divides • 2 Identical daughter cells form with the SAMEnumber of chromosomes as parent cell Occurs during Telophase
MITOSIS END RESULT: Produces 2 Genetically Identical Diploid Body (Somatic) Cells
Cytokinesis • ANIMAL CELL • PLANT CELL
MEIOSIS REPRODUCTION OF SEX CELLS PRODUCES 4 GENETICALLY DIFFERENT HAPLOID GAMETES
Interphase • Cell Grows & Divides • DNA is Replicated
Meiosis I Anaphase I Telophase I Prophase I Metaphase I
2 Stages of Division Meiosis II Prophase II Metaphase II Anaphase II Telophase II
Crossing Over Synapsis/Tetrad = Homologous Chromosomes Pair Up & Cross Over • Crossing Over begins during Prophase I& ends during Anaphase I • Crossing Over is important because • It increases Genetic Diversity • It ensures that all cells produced during meiosis are Different • It Unlinksgenes
Homologous Chromosomes Pair Up & Cross Over Homologous Chromosomes Line Up In The Middle (double line)
Meiosis I Homologous Chromosomes Separate
Spindle Reforms & Chromosomes Attach Chromosomes Line Up in the Middle (single line) Sister Chromatids Separate
Meiosis II Produces 4 Genetically Different Haploid Gametes (Sex Cells)
1ovum (egg) produced 4 sperm produced Fertilization Zygote
Human Gametes normally have 23chromosomes. Human Body Cells normally have 46chromosomes (23pairs).
What is this disorder called? Down’s SyndromeOR Trisomy 21 This is caused by Nondisjunction. Nondisjunction can occur during Anaphase IOR Anaphase II of meiosis if the chromosomes do not SEPARATEcorrectly.
Stage of Meiosis = Anaphase II Stage of Meiosis = Anaphase I Too Many Chromosomes
Crossing Over Homologous Chromosomes Line Up in the Middle/Equator Chromosomes Line Up in the Middle/Equator Homologous Chromosomes Separate Sister Chromatids Separate Diploid Haploid 4 2 Identical Body Cells Genetically Different Gametes (sex cells)