1. Meiosis
Mrs. Harper
Biology
11/28/17

2. November 29, 2017
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3. DO NOW 11/29/17 How many cells are produced during mitosis?
Are they genetically different or identical?
3. What type of cells are produced during mitosis? (somatic body cells or sex cells)
4. List the phases of mitosis in the correct order.
5. What occurs during each phase of mitosis?
6. Define cytokinesis.

4. Division That Produces Sex Cells
Meiosis –
Division That Produces Sex Cells
Why do you share some but not all characters of each parent?
What are the rules of this sharing game?
At one level, the answers lie in meiosis.

5. Reduction-Division Genetic Recombination
MEIOSIS
Reduction-Division
Genetic Recombination

6. Meiosis
The form of cell division by which GAMETES or sex cells are produced.
GAMETES are sperm or egg cells.
Gametes have HALF the # of chromosomes.
Haploid- contains half the amount of chromosomes
Diploid- contains full set of chromosomes

7. Meiosis Continued DIPLOID (2n)  HAPLOID (n)
Meiosis is involved in SEXUAL reproduction.
TWO divisions (MEIOSIS I and MEIOSIS II).

8. Interphase Cell grows and DNA replicates
Occurs before meiosis I, but not meiosis II
Cell grows and DNA replicates

9. Meiosis I
Cell division that reduces the chromosome number by one-half.

10. Homologous Chromosomes
Pair of chromosomes (maternal and paternal) that are similar in shape and size.
Homologous pairs (tetrads) carry GENES controlling the SAME inherited traits.
Humans have 23 pairs of homologous chromosomes:
First 22 pairs are autosomes
23rd pair is sex chromosomes

11. Homologous Chromosomes
eye color
locus
hair color
Paternal
Maternal

12. Sex Chromosomes
XX chromosome - female
XY chromosome - male

13. MEIOSIS I
Homologs separate
Meiosis I

14. Prophase I Nuclear envelope disappears/Chromosomes coil
Synapsis (pairing) occurs
Tetrads form & Crossing over occurs
centrioles
spindle fiber
aster
fibers
TETRAD

15. Genetic Recombination
Tetrad
nonsister chromatids
chiasmata: site of crossing over
variation

16. Metaphase I Homologous chromosomes line up in the middle.
Independent assortment occurs – chromosomes separate randomly

17. Anaphase I Homologous chromosomes pull apart.
Sister chromatids remain attached

18. Telophase I Each nucleus has haploid set of chromosomes.
Cytokinesis occurs & two haploid daughter cells are formed.

19. Sister Chromatids Separate
MEIOSIS II
Sister Chromatids Separate
Meiosis II

20. Meiosis II No Interphase II No DNA Replication
Meiosis II is similar to mitosis

21. Prophase II Same as Prophase in mitosis
Chromosomes condense & Spindle forms

22. Metaphase II Same as Metaphase in mitosis
Chromosomes line up in the middle

23. Anaphase II
Same as Anaphase in mitosis
SISTER CHROMATIDS pull apart

24. Telophase II Same as Telophase in mitosis. Nuclei reform
CYTOKINESIS occurs.
Final product of meiosis:
FOUR HAPLOID daughter cells that are all genetically different
Called GAMETES (eggs and sperm)

25. Meiosis Video https://www.youtube.com/watch?v=D1_-mQS_FZ0 Or

26. Assignment
Complete the worksheet silently and independently on CODE RED
Unfinished classwork is homework