1. Meiosis Guided Notes

2. Interphase…
Prior to prophase I, the cell goes through cell growth and DNA replication during ________________.
interphase

3. Prophase I (chapter 10) condensed homologue homologous pairing
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.
homologue
homologous pairing

4. Prophase I (cont.) synapse crossing over homologous
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.
synapse
Crossing over
crossing over
homologous

5. So why is Crossing Over SO important?????
Reasons why:
crossing over is important because it results in new combinations of genes the that are different from either parent, contributing to genetic diversity.

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

7. Metaphase I Homologous chromosomes Homologous chromosomes
__________________________ 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 ____________________.
Homologous chromosomes
Homologous
chromosomes

8. Anaphase I opposite equal independent genes
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!
opposite
equal
independent
genes

9. Telophase I
Chromosomes reach the opposite ends of the ___________, new nuclei form in each new cell, and spindle fibers ________________.
These new cells are called daughter cells.
cell
disappear

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
__________________!!!)
Meiosis
Meiosis
chromosomes

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

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

14. Anaphase II chromatids The sister ___________ separate.
The cell starts to __________ apart
separate

15. Telophase II – Cytokinesis
The cell pulls _____________ apart – forming new nuclei, one in each cell
Cytokinesis reaches completion, creating ___ haploid ____________ cells
fully 4
daughter

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 _______________________.
gametes 1
polar
oogenesis 4
spermatogenesis

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

18. Meiosis Is related to sexual reproduction.
Is a biological process that creates a new organism by combining the genetic material of two organisms in a process that starts with meiosis.
The union of cells produced by meiosis (gametes) is called fertilization which creates a zygote.