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Use pages 323 to 325 to Define, understand and model meiosis Name Per The last unit explored mitosis, the division of somatic (body) cells, such as skin, bone, blood, to create two identical daughter cells allowing for growth, replacement, and repair in multicellular organisms. The next learning objective includes understanding meiosis, a similar process necessary for the division of sex cells, such as sperm and eggs. Where the goal of mitosis was to create two genetically identical daughter cells, the goal of meiosis is to produce sperm or eggs, also known as gametes. The resulting gametes are not genetically identical to the parent cell. Gametes are haploid cells, with only half the DNA present in the diploid parent cell (germ cell) Achieving the goal of meiosis requires a two-step process to separate homologous chromosomes in a diploid cell. Homologous refers to corresponding chromosomes in a cell – one is maternal (from mom) and one is from paternal (from dad). When these chromosomes are duplicated during the process of DNA replication in interphase they from sister chromatids- matching pairs. If the germ cell begins with 46 chromosomes, how many chromosomes are present after DNA replication in interphase? The four chromosomes together (2 matching maternal and two matching paternal) form a tetrad. The diploid cells of most adult organisms contain two complete sets of inherited chromosomes (one from mom and one form dad) and two complete sets of genes. For humans the diploid number is 46. The goal is the make haploid, or sex cells with half the number or only one set of chromosomes, or haploid. For humans the haploid number is 23. Labeling: Based on the information provided label the homologous pair, sister chromatids (use twice), centromere, the name of the process and fill in the corresponding gene locations after DNA replication. Organize the above information into two column notes – main idea - left and supporting details & vocabulary - right Main Idea Supporting details- Use a dash – for supporting details and a dot for examples * Draw meiosis and trace the homologous chromosomes of an organism with a diploid number of six. The chromosomes need to be color coded to show homologous relationship (two separate colors), Sister chromatids (same color after duplication). Be detailed- nuclear envelop, spindle fibers, centrosomes, centrioles, etc. Choose two gene locations (gene loci) to trace through the division. Also, record the number of chromosomes at each stage and if it is diploid, haploid (or neither). Summarize the events of each stage Meiosis I Drawing # Phase: Interphase Event Name & Details Phase: Cells are Neither diploid or haploid Phase: Prophase I Phase: Cells are: Phase: Phase: Cells are Phase: Phase: Phase: Cells are & Phase: Cells are & Meiosis II Drawing # Event Name & Details Phase: Prophase II Phase: Cells are Phase: Phase: Cells are Phase: Phase: Cells are Phase: & Phase: Cells are & Questions: RSQ 1. What is the goal and result of mitosis? 2. What types of cells undergo mitosis? 3. What is the goal and result of meiosis? 4. What type of cells go through meiosis? 5. What is a zygote and how is it created? Is the zygote diploid or haploid? 6. As the zygote begins to divide into a blastocyst, embryo and then fetus the type of cell division is Practice – Write the appropriate phase in the blank 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. Tetrads line up in the middle of the cell Sister chromatids line up in the middle of the cell Tetrads begin to separate to the opposite side of the cell How many cells are created after meiosis 1? Tetrads condense and are visible ` Nuclear envelop has disappeared between interphase and . Nuclear envelop begins to reform around the sets of sister chromatids . Sister chromatids begin to pull apart toward opposite ends of the cell . The pinching off and creation of 4 haploid daughter cells Individual chromosomes have separated and are at the far ends of the cell . Tetrads have separated into sister chromatids and are at the far end of the cell. The cell is just beginning to move into cytokinesis . 12. How many cells are created after meiosis II? Are they haploid or diploid? 13. Are they identical? Fill in the diploid and haploid number for the following organisms Diploid 14. A carrot has 18 chromosomes in all somatic cells 15. Humans have 46 chromosomes in all somatic cells 16. A fruit fly has 8 chromosomes in all somatic cells 17. A dolphin has 44 chromosomes in all somatic cells Quiz your table buddy – Score Haploid