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.

This process is called Binary Fission 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

REPRODUCTION OF BODY CELLS PRODUCES 2 IDENTICAL DIPLOID CELLS MITOSIS REPRODUCTION OF BODY CELLS PRODUCES 2 IDENTICAL DIPLOID CELLS

Interphase Cell Grows & Prepares for Division DNA is Replicated

Prophase Nuclear Membrane & Nucleolus Disappear SPINDLE FORMS Chromosomes become visible Nuclear Membrane & Nucleolus Disappear SPINDLE FORMS 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

Occurs during Telophase Cytokinesis Cytoplasm Divides 2 Identical daughter cells form with the SAME number of chromosomes as parent cell Occurs during Telophase

Produces 2 Genetically Identical Diploid Body (Somatic) Cells 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 & Prepares for Division DNA is Replicated

Meiosis I Prophase I Metaphase I Anaphase I Telophase I

Meiosis II 2 Stages of Division Prophase II Metaphase II Anaphase II HAPLOID 4 Prophase II Metaphase II Anaphase II Telophase II

Synapsis/Tetrad = Homologous Chromosomes Pair Up & Cross Over 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 Unlinks genes

Homologous Chromosomes Pair Up & Cross Over Homologous Chromosomes Line Up In The Middle (double line)

Homologous Chromosomes Separate Meiosis I Homologous Chromosomes Separate

Spindle Reforms & Chromosomes Attach Chromosomes Line Up in the Middle (single line) Sister Chromatids Separate

Produces 4 Genetically Different Haploid Gametes (Sex Cells) Meiosis II Produces 4 Genetically Different Haploid Gametes (Sex Cells)

1 ovum (egg) produced 4 sperm produced Fertilization Zygote

Karyotype: Male or Female?

Karyotype: Male or Female?

Human Gametes normally have 23 chromosomes. Human Body Cells normally have 46 chromosomes (23 pairs).

What is this disorder called? Down’s Syndrome OR Trisomy 21 This is caused by Nondisjunction. Nondisjunction can occur during Anaphase I OR Anaphase II of meiosis if the chromosomes do not SEPARATE correctly.

Stage of Meiosis = Anaphase I Stage of Meiosis = Anaphase II Too Many Chromosomes

Homologous Chromosomes Line Up in the Middle/Equator 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)