1. Meiosis
By: Aya El-Ghajiji IFY

2. Meiosis Human body cells have 46 chromosomes.
Each parent contributes 23 chromosomes.
It produces sex cells (gametes): egg and sperm.
One cell becomes 4 NON-IDENTICLE cells

4. Genetic Terms Chromosome Chromatin Chromatid Sister chromatids
Homologous pair

5. Chromosome
Structure of DNA in nucleus providing genetic information.

6. chromatin
The material of which chromosomes are made = DNA + histone proteins.

7. Chromatid
Chromosome copy. One pair of replicated chromosomes found during Interphase.

8. Sister chromatids
Identical copies of one chromosome.

9. Homologous pair
Pair of chromosome each coding for the same characteristics originally from the male parent and one from the female parent.

10. WHY DO WE NEED MIOSIS?
To maintain the same number of chromosomes from generation to generation.
Human gametes contain 23 chromosomes.
A cell with n chromosomes is called a
haploid cell.
A cell that contains 2n chromosomes is called a
diploid cell.

11. Meiosis

12. Meiosis I Interphase Chromosomes replicate Centriole pair replicates.

13. Meiosis I Prophase I Chromatin condense
Pairing of homologous chromosomes
Each chromosome consists of two chromatids.
The nuclear membrane breaks down.
Spindles form.

14. Meiosis I
Prophase I
Crossing over produces exchange of genetic information.
Crossing over—chromosomal segments are exchanged between a pair of homologous chromosomes.

15. Meiosis I Metaphase I Homologous chromosomes line up at the equator.
Chromosome centromeres attach to spindle fibers.

16. Meiosis I
Anaphase I
Homologous chromosomes separate and move to opposite poles of the cell.

17. Meiosis I Telophase I The spindles break down. The cell divides.
Cytokinesis

18. Meiosis II
Prophase II
Spindle apparatus forms
chromosomes condense.

19. Meiosis II Metaphase II
A haploid number of chromosomes line up at the equator.

20. Meiosis II
Anaphase II
The sister chromatids are pulled apart at the centromere by spindle fibers and move toward the opposite poles of the cell.

21. Meiosis II Telophase II
The chromosomes reach the poles, and the nuclear membrane and nuclei reform.

22. Meiosis II
Cytokinesis results in four haploid cells, each with n number of chromosomes.

23. The Importance Of Meiosis
It results in genetic variation

24. http://www.youtube.com/watch?v=kVMb4Js 99tA
Meiosis
99tA

25. Quiz A human cell containing 22 autosomes and a Y chromosome is
A zygote
A sperm cell
An ovum

26. Quiz
Homologous chromosomes segregate toward opposite poles of a dividing cell during
Mitosis
Meiosis I
Meiosis II

28. Bibliography
BAKER, M., INDGE, B., & ROWLAND, M. (2001). Further studies in biology. London, Hodder & Stoughton.
CAMPBELL, N. A. (1996). Biology. Menlo Park, Calif, Benjamin/Cummings Pub. Co.
Llopis-Garcia, R., (2012) Meiosis Notes. City of Bath College.
PARSONS, R. (2009). AS & A2 Biology: complte revision guide and practice : exam board AQA. Kirkby-in- Furness, Coordination Group.
TOOLE, G., & TOOLE, S. (2008). AQA biology AS. Cheltenham, Nelson Thornes.