1. Meiosis Chapter 8

2. Two Types of Reproduction
Asexual Reproduction
1 parent
Identical DNA
Process: Mitosis
Sexual Reproduction
2 parents
Different DNA
Combo of 2 organisms
Process: Meiosis

3. DNA

4. Homologous Chromosomes chromosomes with the same genes

5. Chromosome # Diploid Haploid homologous chromosomes Complete set
Body cells
Haploid
One member of pair
½ set
Gametes
Egg or Sperm

6. Fertilization 23 46 23 Fertilized egg – zygote
process by which an egg and sperm unite 23
Zygote develops into embryo (early stage of development) and finally adult organism by mitosis 46
Haploid 23
Fertilized egg – zygote
Diploid

7. Fertilized egg – zygote
Without meiosis …………
Fertilized egg – zygote 46 92 46

8. Meiosis: A reduction division

9. Prophase I Chromosomes condense Nuclear envelope breaks Spindle forms
Tetrads form

10. Tetrads
A pairing of homologous chromosomes
Four chromatids

11. Prophase I Crossing over occurs Exchange genetic material Why?
Increase variation

12. Metaphase I
Tetrads line up in the middle of the cell

13. Anaphase I
Tetrads separate & chromosomes move towards poles

14. Telophase I Nuclues reforms Spindle dissappears
Two new cells are formed

15. Meiosis II: Reducing Chromosome Number

16. Results of Meiosis Gametes (egg & sperm) form
Four haploid cells with one copy of each chromosome
Different combinations of alleles due to crossing over
GENETICALLY DIFFERENT

17. Sperm Formation

18. Egg Formation (unequal cytokinesis)

19. Mitosis Vs. Meiosis Characteristic Mitosis Meiosis #divisions 1 2
#daughter cells 4
Ploidy beginning
Diploid
Ploidy end
Haploid
Purpose
Growth/replace
Reproduction
Where occurs?
Body cells (Somatic)
Gametes