1. Chapter 11.4 (Pg. 323-329): Meiosis

2. Chromosome Number - Is how many chromosomes a cell has
- Is represented by the letter N
- Can be either haploid or diploid
Changes during S phase of interphase, and during cell division

3. Chromosome Number - Diploid A cell has two copies of each chromosome
Is written as 2N
These two copies are homologous
One set came from each parent
Have the same genes in the same locations
Diploid cells are created by mitosis

5. Chromosome Number - Haploid
A cell has one copy of each chromosome
Is written as N
Most often occurs in gametes
Haploid cells are created by meiosis
Haploid sperm can combine with a haploid egg to make a diploid zygote, or fertilized egg

7. Phases of Meiosis Occur in two stages, Meiosis I and Meiosis II
Each contains prophase, metaphase, anaphase, telophase, and cytokinesis
Interphase occurs before Meiosis I, but not before Meiosis II

9. Meiosis I Interphase DNA is copied during S phase of Interphase
Organelles and molecules are copied to prepare for cell division

10. Meiosis I - Prophase I - Spindle forms - Nuclear membrane disappears
- Chromosomes condense
- Homologous chromosomes pair up
- Forms a tetrad
Homologous chromosomes cross over
Chromatid on one chromosome swaps a section with another
This creates genetic variation

13. Meiosis I
- Metaphase I
- Homologous chromosomes line up across the center of the cell

15. Meiosis I
- Anaphase I
Spindle fibers pull each homologous chromosome pair towards opposite ends of the cell

17. Meiosis I Telophase I and Cytokinesis
A nuclear membrane forms around each cluster of chromosomes
Spindle disappears
The cell membrane pinches in to separate the cytoplasm into two haploid daughter cells

19. Meiosis II - Prophase II Chromosomes condense
Nuclear membranes disappear
Spindles form

20. Meiosis II Metaphase II
Chromosomes line up along the middle of the cell

21. Meiosis II - Anaphase II
Individual chromatids move to opposite sides of the cell

23. Meiosis II Telophase II and Cytokinesis Nuclei re-form
The cell membrane pinches in to separate the cytoplasm into four genetically unique haploid daughter cells

28. Differences Between Mitosis and Meiosis
Makes genetically identical cells
Makes diploid cells
Maintains the original chromosome number
Makes two daughter cells
Uses only one cell division
No pairing of homologous chromosomes
Only separates sister chromatids
No crossing over occurs
Used for many cellular processes
Makes genetically unique cells
Makes haploid cells
Reduces the chromosome number by half
Makes four daughter cells
Uses two cell divisions
Pairs homologous chromosomes together
Separates homologous chromosomes, then sister chromatids
Crossing over occurs
Only makes gametes for reproduction

29. Linked Genes
Alleles of different genes tend to be inherited together from one generation to the next when those genes are located on the same chromosome
Can be shown with a gene map
Indicates the location of each gene on a chromosome