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Meiosis Notes
Now…let’s review chromosomes!
Steps of Meiosis:• Meiosis is made of two parts: Meiosis I and Meiosis
II• First: BEFORE meiosis occurs, there is the “IN
BETWEEN PHASE”• Before Meiosis = INTERPHASE• First Part: Meiosis I!• Prophase I (CROSSING OVER OCCURS HERE!)
• Metaphase I• Anaphase I (HOMOLOGOUS CHROMOSOMES ARE SEPARATED)
• Telophase I• Cytokinesis
Steps of Meiosis:• Second Part: Meiosis II!
• Prophase II • Metaphase II• Anaphase II (SISTER CHROMATIDS ARE SEPARATED)
• Telophase II• Cytokinesis
Prophase 1
• Chromosomes become visible and the nuclear membrane breaks apart
• Crossing over occurs!
• Creates new gene combinations!
Metaphase 1 vs. 2
• Metaphase 1- homologous chromosomes pair up in the middle
• Metaphase 2- single chromosomes line up in the middle
Anaphase 1 vs. 2
• Anaphase 1- homologous chromosomes separate and move apart
• Anaphase 2- Chromatids separate and move apart
Telophase 1 vs. 2
• Telophase 1- Single cell splits into 2 cells, goes right into Prophase 2
• Telophase 2- Two cells each split, creating 4 haploid cells
Meiosis: A Second
Look
• Meiosis results in 4 genetically different haploid daughter cells
One major point!
*These cells are sperm and eggs!
Fertilization
n n+ = 2n
Haploid Egg cell
23 chromosomes
Haploid Sperm cell
23 chromosomes
DiploidZygote
46 chromosomes
Questions:What are some similarities between MITOSIS
and MEIOSIS?What are some differences between MITOSIS
and MEIOSIS?Why do organisms need to go through
mitosis?Why do organisms need to go through
meiosis?Which organisms undergo mitosis?Which organisms undergo meiosis?
Prove You Know It!1.What is the name of the
process that creates gametes?2.What is the difference
between a HAPLOID cell and a DIPLOID cell?
3.What are the two main parts of meiosis?