1. Meiosis

2. I. Definition
Cell division that produces cells with half of the number of chromosomes as the parents cells

3. II. The Purpose of Meiosis
A. Produce gametes (sex cells)
Ex: sperm and eggs
B. Start with 1 diploid (2n) cell &
make 4 haploid (n) cells
C. Keep the number of chromosomes
constant for a species

4. double, divide and divide again
III. Meiosis Summary
double, divide and divide again

5. IV. Stages of Meiosis: A. Interphase
G1 stage: growth
S stage:
synthesis of DNA
G2 stage: further growth

6. B. Prophase I
chromatin coils up & pairs of sister chromatids (tetrads) become visible.
Crossing over occurs

7. C. Metaphase I
tetrads line up at the equator

8. D. Anaphase I
tetrads split & pairs move to opposite poles

9. E. Telophase I chromatids uncoil Ends with Cytokinesis
2 new diploid (2n) cells

10. F. Prophase II
chromatin coils up & the sister chromatids become visible

11. G. Metaphase II:
sister chromatids line up at the equator

12. H. Anaphase II:
sister chromatids split & the separated chromosomes move to opposite poles

13. I. Telophase II: Chromosomes uncoil into chromatin.
Ends with Cytokinesis:
4 new haploid (n) cells

14. Terms:
Meiosis
Diploid
Haploid
Gamete
Crossing over

15. Genetic Variation
Meiosis is a major source of genetic variation in sexually reproducing organims
Variation occurs in two (2) ways
Crossing over
When homologous pairs are together some information is transferred or exchanged between the chromosomes.
They literally swap parts, usually near the end of a chromosome
Assortment at Metaphase I and II
The way the chromosomes line up at metaphase is random

16. Mitosis Meiosis Similarities Produce Cells IPMAT DNA Replication
Comparison
Meiosis
Similarities
Produce Cells
IPMAT
DNA Replication
How Different
Somatic Cells
Location
Gonads 1
Number of Division 2 2n
Final # of Chromosomes 1n
Final # of Cells 4
Growth, repair etc
Purpose of Product
Reproduction
Conclusion
Cells are produced

17. Meiosis so My chromosomes are Happy