Bell Ringer Cell Division Review Units 5 6

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 This process is called Binary Fission

This is the Cell Cycle M Phase

Eukaryotic Somatic (Body) Cell Division = Mitosis • Interphase Stages of Cell Cycle – G 1 = Growth – S = DNA replication – G 2 = 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 EARLY LATE • Chromosomes become visible • Nuclear Membrane & Nucleolus Disappear

Metaphase • Spindle Fibers attach to the Centromeres • Chromosom es 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 Occurs during Telophase • Cytoplasm Divides • 2 Identical daughter cells form with the SAME number of chromosomes as parent cell

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 Prophase I Metaphase I Anaphase I Telophase I

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

Synapsis/Tetrad = Homologous Chromosomes Pair Up & Cross Over Crossing 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)

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)

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 can occur during Anaphase I OR Anaphase II of meiosis if the chromosomes do not SEPARATE correctly.

Stage of Meiosis = Anaphase II Too Many Chromosomes

Crossing Over Chromosomes Line Up in the Middle/Equator Sister Chromatids Separate Diploid 2 Homologous Chromosomes Line Up in the Middle/Equator Homologous Chromosomes Separate Haploid 4 Identical Body Cells Genetically Different Gametes (sex cells)