1. CHAPTER 11: INTRODUCTION TO GENETICS Standards B.1.8, B.1.21, B.1.28, B.1.29 Section 11.4: Meiosis

2. ASEXUAL REPRODUCTION SEXUAL REPRODUCTION

3. SO, Where does the baby get its genetic material? Sexual Reproduction = 2 Parents

4. Section 11.4: Meiosis  IMPORTANT CONCEPT: Because organisms get half of their chromosomes from mom and half from dad, the chromosomes from each parent MUST be divided in half before they can be passed on.

5. Section 11.4: Meiosis  Homologous Chromosomes  A matching pair of chromosomes that have the same genes. One of these chromosomes comes from MOM. The other chromosome comes from DAD.  Every animal has a unique # of chromosomes.  Humans have 46 chromosomes. (23 from MOM, 23 from DAD)

6. Section 11.4: Meiosis  Diploid Cell  A cell that contains BOTH sets of chromosomes (mom AND dad). (2 sets = diploid = 2N)  All body cells!  Haploid Cell  A cell that contains ONE set of chromosomes (mom OR dad). (1 set = haploid = 1N)  All sex cells!

7. Section 11.4: Meiosis  Meiosis  The process of reduction division in which the number of chromosomes in a cell is cut in half.  Homologous chromosomes are separated in the process.  mom! dad! 

8. Section 11.4: Meiosis There are TWO major divisions during meiosis.  Meiosis I  Reduction Division  Homologous chromosomes pair up to form tetrads.

9. Section 11.4: Meiosis  Meiotic “Crossing Over”  Crossing over: The exchange of alleles between homologous pairs while in tetrads.  Chromosomes “trade” information!  **Increases Diversity**

10. Section 11.4: Meiosis There are TWO major divisions during meiosis.  Meiosis II  This happens the SAME way as Mitosis!  During Meiosis II, the sister chromatids are pulled apart.  This results in 4 haploid daughter cells.

11. Meiosis II This happens the SAME way as Mitosis! During Meiosis II, the sister chromatids are pulled apart, resulting in 4 haploid daughter cells.

12. Section 11.4: Meiosis Results in 2 genetically identical diploid cells. Allows organisms to grow and replace parts. Results in 4 genetically different haploid cells. Sex cell (gamete) production. MITOSISMEIOSIS