Meiosis Chapter 8 Notes PDF
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These notes detail the process of meiosis, a type of cell division that results in the production of gametes. It explains the different phases, including interphase, meiosis I and II, and cytokinesis. The notes cover topics such as homologous chromosomes, tetrads, crossing over, and the differences between spermatogenesis and oogenesis. Additional information on important concepts is also included, such as the purpose and process of mitosis and meiosis, independent assortment, and the role of meiosis in genetic variation.
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MEIOSIS CHAPTER 8 NOTES I can describe the purpose of meiosis, and identify the types of cells that undergo this process. I can draw and define homologous chromosomes. I can describe diploid and haploid cells in terms of chromosome number. I can describe the overall process of meio...
MEIOSIS CHAPTER 8 NOTES I can describe the purpose of meiosis, and identify the types of cells that undergo this process. I can draw and define homologous chromosomes. I can describe diploid and haploid cells in terms of chromosome number. I can describe the overall process of meiosis, including the number of chromosomes in cells before and after meiosis takes place. I can identify the following points in meiosis: – When homologous chromosomes separate – When sister chromatids separate – When chromosome number is reduced from diploid to haploid. I can identify the number and types of cells formed during spermatogenesis and oogenesis. – Describe what a polar body is. I can describe when during meiosis Mendel’s Law of Independent Assortment takes place. I can differentiate between the purpose and process of mitosis and meiosis. Include: – Purpose – Types of cells that undergo process – How many times DNA replicates – How many rounds of division – Number of daughter cells produced – Chromosome # compared to beginning cell (haploid or diploid) I can draw a picture of crossing over. I can describe when it occurs during meiosis and how it increases genetic variation. I can identify a tetrad. I can explain how sexual reproduction provides variation in a population. Definition of meiosis: a process of reduction division that produces gametes in which the number of chromosomes per cell is cut in half (haploid) through the separation of homologous chromosomes. Homologous chromosomes: chromosome “twins” that resemble each other in length, centromere position and have the same genes (although may have different versions of the gene). chromosomes that have a corresponding chromosome from the opposite-sex parent. T t G G a A A cell that contains both sets of homologous chromosomes is diploid, which means “two sets”. (2n) A cell that contains only one set of chromosomes (one member of each homologous pair) is haploid. (n) Remember the cell cycle: Interphase Meiosis I and Meiosis II Cytokinesis INTERPHASE: just like interphase before mitosis G1: cell grows, protein production S: DNA replication G2: productions of new organelles including centrioles MEIOSIS I: PROPHASE I: Chromatin coils into chromatids and the homologous pairs of duplicated (doubled) chromosomes come together to form a tetrad. Crossing over occurs when portions of the homologous chromosomes are exchanged. The rest of prophase is very similar to mitosis. Why is crossing over so important? Crossing over allows for the random mixing of genes (genetic recombination) which adds genetic variety to a species so that no two individuals are exactly the same. METAPHASE I: Tetrads line up at the equator of the spindle (cell) and assort independently. Independent Assortment Originally from DAD Originally from MOM Independent Assortment Originally from DAD Originally from MOM Independent Assortment Originally from DAD Originally from MOM Independent assortment: Original chromosomes from mom (maternal) and dad (paternal) can line up randomly and independent of each other on either side of the equator. Why is independent assortment so important? Independent assortment allows for the random mixing of genes (genetic recombination) which adds genetic variety to a species so that no two individuals are exactly the same. ANAPHASE I: Homologous chromosomes separate and are pulled to the poles (the centromeres do NOT split). What is the third source of variation in a population provided by sexual reproduction? During anaphase I, homologues segregate into different cells, so that gametes will possibly have different versions for the same gene. TELOPHASE I: Chromosomes uncoil, spindle breaks down. The nuclear membranes and nucleoli reform. Cytoplasm divides (cytokinesis) to form two cells. NOTE: There is NO interphase between meiosis I and meiosis II. Why is this important? So that each new cell will only have half (haploid) the number of chromosomes as the original parent cell. PROPHASE II: *just like mitosis METAPHASE II: except that there ANAPHASE II: is only half the TELOPHASE II/ number of CYTOKINESIS: chromosomes. Prophase II Metaphase II Anaphase II Telophase II Spermatogenesis vs Oogenesis: Spermatogenesis: 4 sperm cells during spermatogenesis. Oogenesis: 1 egg cell and 3 polar bodies during oogenesis. Polar bodies are the other daughter cells produced during meiosis, but don’t have as much cytoplasm since the egg cell gets most of it, so they appear much smaller. They are “discarded” by the body (broken down and reabsorbed). Next is random fertilization: Haploid egg + haploid sperm = diploid zygote What is the end result of meiosis? Four genetically different haploid cells that contain half the number of chromosomes as the original parent cell. What was the end result of mitosis? Two genetically identical diploid cells that are identical to the original parent cell.
