1. Meiosis Guided Notes
Ramshaw – Biology

2. Interphase…
Interphase happens at the start of _____________ as well as mitosis.
Prior to prophase I, the cell goes through the G1, S, and G2 phases of ________________.

3. Prophase I (chapter 10)
DNA coils into ___________ chromosomes, spindle fibers appear, nucleus disappears.
Every chromosome is paired up next to its ______________ (the chromosome that is the same size and shape).
This is called _____________ and does not occur in mitosis.

4. Prophase I (cont.)
Each pair of homologous chromosomes is called a ______________.
When chromosomes line up next to each other, “____________ ______” occurs and they exchange pieces of DNA.
This is called _________ recombination.
Crossing over
Only one cross over is shown
but many occur per pair.

5. So why is Crossing Over SO important?????
Reasons why:

6. Review of Key Terms Homologue (Homologous Chromosomes): Synapsis
Tetrad
Crossing Over

7. Metaphase I
_____________ line up in the center of the cell next to each other.
Spindle fibers from one centriole attach to the centromere of one _________ chromosome then spindle fibers from the opposite centriole attach to the other homologous _____________.

8. Anaphase I Each homologous chromosome moves to the _____________ pole.
This __________ separation of homologous chromosomes is called ________________ assortment.
It separates the chromosomes you inherited from your mom and dad and creates new combinations of ________ on each chromosome!

9. Telophase I
Chromosomes reach the opposite ends of the ______, new nuclei form in each new cell, and spindle fibers __________.
The new cells are ___________!

10. To review… What are the major events in Meiosis I?… Prophase I:
Metaphase I:
Anaphase I:
Telophase I:

11. NO INTERPHASE HERE
There is no interphase between _____________ 1 and ____________ 2. This is very important because there is no S phase!!! (no doubling of the ________!!!)

12. Start of Meiosis II Prophase II
Centrioles form and move toward the __________
The nuclear membrane ________________

13. Metaphase II
__________ fibers attach from the centrioles to the centromeres
The __________ chromatids line up along the cell equator

14. Anaphase II The centromeres __________ and sister chromatids separate
The cell starts to ______ apart

15. Telophase II – Cytokinesis
The cell pulls _____________ apart – forming new nuclei, one in each cell
Cytokinesis reaches completion, creating ___ haploid ____________ cells

16. These 4 haploid cells then create:
______________!
If the organism going through meiosis is a female, only ___ of the cells becomes the egg, the others become “_______ Bodies” and are dissolved by the body. This process of making an egg is called __________________.
If the organism going through meiosis is a male, _____ __ cells become spermatids which mature in to sperm. This is called _______________________.

17. Major events in Meiosis!
The cell starts out by doubling the _____ in Interphase:
After S1 phase
(Sister chromatids)
Copy of Chromosome
(doubling the DNA)
A chromosome before
the S1 phase
Original
Chromosome

18. After Interphase is… Prophase I _____________ and crossing over occur
Lets draw that out!

19. Then comes:
Metaphase I – Homologous chromosomes line up in the _________ of the cell next to each other.
Anaphase I – The __________ are pulled apart, one to each side of the cell
Telophase I – Two ___________ cells are formed

20. Then the second part - Meiosis II
Prophase II – Nucleus _______________
Metaphase II – Chromosomes line up _________ file down the middle of the cell
Anaphase II – Sister chromatids are pulled ___________ towards opposite ends of the cell
Telophase II – 4 __________ cells are formed