1. Chapter Meiosis

2. Meiosis Vocabulary Diploid Haploid Gametes Homologous chromosomes
Crossing over
Tetrad

3. So lets talk about making a person
So who do you look like?
What holds the genetic information?
How is this genetic information passed to the next child?
How many sets of chromosomes do you have?
What are homologous chromosomes?
Where do you get your sets of chromosomes?

4. Meiosis Most cells have two sets of chromosomes
This is called diploid (2 sets of 23)
2n = diploid #, humans 2n = 46
Gametes have one set of chromosomes
This is called haploid cell (1 set of 23)
n = haploid #, humans n = 23
Sperm, egg, pollen are examples
Meiosis is the process of making haploid cells from diploid cells
Haploid + haploid = diploid /fertilization

6. Meiosis Meiosis has two divisions Meiosis 1 Meiosis 2
First division separates the homologous chromosomes
Crossing over of genetic material can take place
Meiosis 2
2nd division separates the sister chromatids into individual chromosomes
Process is like mitosis
Except for the number of chromosomes
Each division has same 4 ‘steps’
Prophase, metaphase, anaphase, telophase

9. Figure 11-15 Meiosis Meiosis I Interphase I Section 11-4 Prophase I
Metaphase I
Anaphase I
Cells undergo a round of DNA replication, forming duplicate Chromosomes.
Each chromosome pairs with its corresponding homologous chromosome to form a tetrad.
Spindle fibers attach to the chromosomes.
The fibers pull the homologous chromosomes toward the opposite ends of the cell.
Go to Section:

10. Figure 11-17 Meiosis II Meiosis II Section 11-4 Prophase II
Metaphase II
Anaphase II
Telophase II
Meiosis I results in two haploid (N) daughter cells, each with half the number of chromosomes as the original.
The chromosomes line up in a similar way to the metaphase stage of mitosis.
The sister chromatids separate and move toward opposite ends of the cell.
Meiosis II results in four haploid (N) daughter cells.
Go to Section:

12. Mitosis vs Meiosis Mitosis Meiosis 1 division 2 daughter cells
Exact copies of parent cells
Diploid to diploid
Purpose
Growth
Repair
Asexual reproduction
Meiosis
2 divisions
1st separates pairs
4 daughter cells
Each unique
Diploid to haploid
Purpose
Make gametes/ sex cells
Leads to genetic variation due to crossing over