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Explore the intricate process of meiosis, its stages, and significance in creating genetically diverse cells. Learn about the differences between mitosis and meiosis in an engaging video format. Bring your own device, take notes, and deepen your understanding.
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To be successful today… Pick up graded Notebooks Pull out why meiosis notes BYOD Color of the day is Phones are in put away in backpacks
After warm up: Add to TOC & Glue in pages • NOTES: Why Meiosis? • NOTES: Stages of Meiosis • NOTES: Stages of Meiosis
MEIOSIS 46 chromosomes 46 chromosomes Essential Question: How does meiosis differ from mitosis and how does meiosis create cells that are genetically different from the parent cell?
Two Types of Cells 1) Somatic (body) cellsEX: skin, brain, liver, etc 2) Sex cellsEx: Cells in reproductive organs (testes & ovaries) Meiosis occurs in sex cells
Meiosis Interphase I Prophase I Metaphase I Anaphase I Telophase I Prophase II Metaphase II Anaphase II Telophase II
Meiosis takes place in two series of steps & includes TWO Divisions No second Interphase Meiosis I I, P, M, A, T + Meiosis II P, M, A, T Which means…no DNA replication before meiosis II
Interphase I • DNA replicates creating homologous chromosomes
1) PROPHASE I • Homologous chromosomes pair up forming a tetrad (4 chromatids) Images modified from: http://www.emc.maricopa.edu/faculty/farabee/BIOBK/Crossover.gif
2. CROSSING OVER OCCURS • Homologous chromosomes exchange DNA • Creates genetic diversity http://sps.k12.ar.us/massengale/genetics%20tutorial.htm
2) Metaphase I • Tetrads line up in the middle
Meiosis II No Interphase II which means chromosomes are NOT copied again.
7) Anaphase II: chromosomes are pulled to opposite ends of the cell
8) Telophase II / Cytokinesis ~The two cells divide to form 4 genetically different cells (gametes)
End Result of Meiosis • Sex cells begin meiosis diploid (2 copies of each chromosome) • At the end of meiosis, four new cells (gametes)are formed
End Result of Meiosis • Gametes are haploid (half # chromosomes as parent cell) • Gametes will mature into sperm or eggs for sexual reproduction
Mitosis vs Meiosis Diploid Parent Cell Crossing over occurs 2 cell divisions 2 identical, diploid somatic cells 4 genetically different, haploid gametes