1. Chapter 10.2 What Meiosis Does AP Biology Fall 2010

2. Objectives Understand the effect that meiosis has on chromosome number Compare mitosis and meiosis

3. Homologues Meiosis begins with diploid (2n = 46) germ cells and produces haploid gametes (n = 23) In 2n cells, there are 2 chromosomes of each type, called homologous chromosomes Homologous chromosomes line up (even unequally matched sex chromosomes) during meiosis

4. Homologues

5. Each gamete produced by meiosis has one of each pair of homologous chromosomes – Haploid Each pair has the same length, shape, and assortment of genes Haploid Diploid

6. Two Divisions Not One In some ways meiosis resembles mitosis – Chromosomes are duplicated during interphase to form sister chromosomes held together at cetromere – Chromosomes are moved by the microtubules of spindle apparatus

7. Two Divisions Not One Unlike mitosis, meiosis has two series of divisions – Meiosis I and II

8. Two Divisions Not One Meiosis I: homologous chromosomes pair, separate, and cytoplasm divides, giving rise to 2 daughter cells – Each of the two daughter cells receives one set of chromosomes in the duplicated state – Cell is haploid

9. Two Divisions Not One Meiosis II: sister chromatids of each chromosome separate – Cytoplasm divides again, resulting in 4 haploid cells – Each haploid cell has one chromosome (consisting of 1 chromatid) of each type

10. Review 1.State the differences and similarities between meiosis and mitosis.

11. Answers 1.Mitosis: 2n to 2n, one cellular division 2.Meiosis: 2n to n, two cellular division