1. Meiosis

2. Chromosome Number
The two sets of chromosomes are homologous, each chromosomes from the male parent has a corresponding chromosome from the female.
Fruit flies have 8 chromosomes.
4 came from the fly’s male parent, and 4 came from the female parent.

3. Diploid & Haploid Diploid: cell with 2 sets of chromosomes.
Diploid: 2N
Fruit Fly: 2N=8 Humans: 2N=46
Haploid: cell with 1 set of chromosomes, i.e. gametes.
Haploid: N
Fruit Flies: N=4 Humans: N=23

4. Meiosis 1 Diploid cell  4 haploid cells Chromosome no. is halved
Separate homologous chromosomes

6. Meiosis I Interphase I: copy chromosomes
Prophase I: pair homologous chromosome, form a tetrad
Metaphase I: spindle fibers attach to chromosome.
Anaphase I: fibers pull homologous chromosomes toward opposite ends.
Telophase I & Cytokinesis: nuclear membranes form. Cell separates into 2 cells.

7. Metaphase I Anaphase I
Telophase I

8. Meiosis II
Prophase II: 2 haploid cells, with ½ the number of chromosomes.
Metaphase II: chromosomes line up in the middle.
Anaphase II: sister chromatids separate and move toward opposite ends.
Telophase & Cytokinesis: result in 4 haploid (N) cells.

11. Mitosis Meiosis 2 Cells Identical Diploid 4 Cells Not Identical
Haploid

12. Gene Linkage Chromosome: group of linked genes.
Traits appear to be inherited together.
Chromosomes assort independently, not genes.

13. Cross-over Cross-over Creates genetic diversity
separate & exchange linked genes
new combination of alleles
Creates genetic diversity

14. Cross-over

15. Gene Maps
The further apart two genes are, the more likely they are to be separated by crossover.
The rate of separation/recombination are used to create a map of the distances between genes.
Gene Map: shows the relevant location of each known gene on a chromosome.

16. Gene Map