MEIOSIS Object: to study the meiosis through its subsequent developmental stages and discuss its Genetics Significant..

Meiosis Meiosis in males is called spermatogenesis and produces sperms. Meiosis in females is called oogenesis and produces ova. Two divisions (meiosis I and meiosis II).

MITOSIS Somatic cells MEIOSIS Cells in sexual cycle 1 cell division: 2 daughter cells 2n 2n MEIOSIS Cells in sexual cycle 2 cell divisions: 4 cells product of meiosis n n n 2n n n n n=chromosome number

definitions Homologous chromosomes: the members of a chromosome pair that is identical in the arrangement of genes

Homologous Chromosomes eye color locus hair color Paternal Maternal

definitions Synapsis: (التشابك) the intimate association ترابط وثيق)) of homologous chromosomes… Homologous chromosomes

definitions Crossing-over: (العبور) a term describing the process of reciprocal chromosomal interchange by which recombinants arise

Crossing over Pairing of homologous chromosomes Chiasma formation Breakage and joining Recombinant

MEIOSIS I Prophase I The longest phase. This phase can be divided into 5 stages; a) Leptotene b) Zygotene c) Pachytene d) Diplotene e) Diakinesis

Prophase I 1. Leptotene 2.Zygotene 3.Pachytene 4.Diplotene 5.Diakinesis Prophase I

Metaphase I Anaphase I Telophase I Prophase II Prophase I

Meiosis 2nd division: like mitosis with haploid set

4 Haploid cells Gametes

Mitosis vs Meiosis Mitosis Meiosis Results in 2 Diploid Cells (2N) 4 Haploid Cells (N) Cells are Genetically Identical Genetically Different Occurs in Somatic (Body) Cells Sex Cells

Slides for Meiosis I & II: Prophase I

Metaphase I:

Anaphase I:

Telophase I:

Prophase II:

Metaphase II:

Anaphase II:

Telophase II:

Final result Mitosis : two genetically identical diploid cells from one diploid parent cell   Meiosis : Four genetically different haploid cells from one diploid parent cell