ZOL 141 1st Edition Lecture 7Outline of Last Lecture II. Review of Mitosis phasesIII. Meiosisa. Diploidb. HaploidOutline of Current Lecture IV. meiosisA. Meiosis 1B. Meiosis 2Current LectureMeiosis- Takes place in germ cells to produce gametes (sperm and egg)- Diploid cells become Haploid- Two successive cell divisions: one cell produces four cellso Male: one cell produces four gametes (sperm)o Female: one functional oocyte and two or three polar bodies- Divided into Meiosis 1 and Meiosis 2o Meiosis 1: reduces chromosome number to haploido Meiosis 2: separates sister chromatids- Meiosis 1o Prophase 1, mtaohase 1, anaphase 1, telophase 1o Cell: Diploid (2n)=4 chromosomes Haploid (n)= 2 chromosomeso Prophase 1: start with replicated chromosomes, two sister chromatids similar to mitosis in that: nuclear envelope begins to disintegrate,_____break down Different from mitosis in that: chromosomes begin to pair up “Crossing over”: chromosomes physically exchange partso Metaohase 1: Pair of homologous chromosomes line up at equatero Anaphase 1: Paired homologous chromosomes separate: homologous chromosomes pulled to opposite ends of cello Telophase: Cells start to separateo Up until anaphase 1 the cells are diploid (four chromosomes with two chromatids each)- Meiosis 2o Prophase 2 (same as mitosis)o Metaphase 2: All chromosomes lined up on one planeo Anaphase 2: Analogous to mitosiso Telophase 2: Cells start to separate- Meiosis produces four gametes- Each is haploid (2 chromosomes)- Each chromosome consists of one
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