LG 8.1-8.3 Meiosis and Gametogenesis PDF

LG 8.1 - 8.3 Meiosis and Gametogenesis Biology 2: Fundamentals of Biology 2, S.Y. 2024-2025 Sept. 23 and 25, 2024  Desired Learning Competencies Compare and contrast mitosis and meiosis Explain all possible sources of variation among daughter cells due to meiosis and...

LG 8.1 - 8.3 Meiosis and Gametogenesis Biology 2: Fundamentals of Biology 2, S.Y. 2024-2025 Sept. 23 and 25, 2024  Desired Learning Competencies Compare and contrast mitosis and meiosis Explain all possible sources of variation among daughter cells due to meiosis and predict their impact on genetic diversity. Explain how one egg and four sperms arise from the meiotic divisions of gametogenesis.  How “UNIQUE” are you? Random Fertilization - 1/2M egg cells x 1/4B sperm cells Independent Assortment - 1/223 unique chromosome combination (for each gamete) Crossing Over - occurs an average of 2-3 times per chromosome pair  What is MEIOSIS? reduction in the number of sets of chromosome from two to one in gametes this process is to counterbalance the doubling during fertilization 1 cell → 4 haploid daughter cells ➔ IMPORTANCE 1. genetic diversity 2. increased the survival of species  The Homologous Chromosomes pair of chromosomes with the same length, centromere, and gene location. ➔ Each one is contributed by each parent. Concept Check  Overview of Meiosis Interphase M phase ○ 2 nuclear division Meiosis I (reduction division) - separation of homologous chromosomes - one diploid cell to two haploid cells Meiosis II (equational division) - separation of sister chromatids - two haploid cells to four haploid cells Overview of Meiosis I Prophase I  Closer Look on CROSSING OVER A A a a Recombinant chromatids Non- recombinant chromatids  Check your understanding! Using the clay in front of you: 1. Designate 1 color for paternal chromosome and another for maternal chromosomes 2. Create 2 sets of homologous chromosomes to symbolize 2n=4 3. Model the crossing over event at q arm and point out the chiasma.  Metaphase I Homologous chromosomes randomly assemble at the metaphase plate through the microtubule. Independent assortment of maternal and paternal chromosomes. In 2n=24, how many chromosomes? Homologous chromosomes?  Independent Assortment during Metaphase I Product Rule of Probability (p+m)n Where: p= paternal chromosomes m=maternal chromosomes n= # of sets of chromosomes Example: If 2n= 4, what is the probability of having a gamete that contains all chromosome that came from the father?  Independent Assortment during Metaphase I Calculating total number of possible chromosomal combinations in gametes: 2n Where: n= # of sets of chromosomes Example: If 2n= 10, How many types of sex cells/ combination of chromosome arrangement will be produced? 25 = 2 x 2 x 2 x 2 x 2 = 32 combinations  Check your understanding! From the homologous chromosomes you created: 1. Model the Metaphase I for 2n=4 where maternal chromosomes comes first before paternal chromosomes.  Anaphase I Separation of the homologous chromosomes towards the opposite poles through the spindle microtubules. The sister chromatids are still attached at the centromere. In 2n=24, how many chromosomes? Homologous chromosomes?  Check your understanding! From the Metaphase I you created: 1. Model the Anaphase I for 2n=4.  Telophase I and Cytokinesis Decondensation of sister chromatids. Reformation of nuclear envelope. Formation of cleavage furrow. 2 haploid daughter cells with duplicated chromosomes. In 2n=24, how many chromosomes for each daughter cell? Homologous chromosomes?  Check your understanding! From the Anaphase I you created: 1. Model the Telophase I and Cytokinesis for 2n=4.  Interphase II (Interkinesis) In some species, chromosomes decondense and nuclear envelope form. Some cells may undergo a period of rest and preparation for the second meiotic division (meiosis II). No chromosome duplication. Overview of Meiosis II  Prophase II Condensation of sister chromatids Formation of new spindle fiber Disintegration of nuclear envelope  Metaphase II Movement of sister chromatids to the metaphase plate in one line. In 2n=24, how many chromosomes ? Homologous chromosomes? chromatids?  Check your understanding! From the Telophase I you created: 1. Model the Metaphase II for 2n=4.  Anaphase II Separation of the sister chromatids towards the opposite poles by the shortening of the kinetochore microtubules while cell lengthening by non-kinetochore microtubules. In 2n=24, how many chromosomes ? Homologous chromosomes? chromatids?  Check your understanding! From the Metaphase II you created: 1. Model the Anaphase II for 2n=4.  Telophase II and Cytokinesis Decondensation of sister chromatids. Reformation of nuclear envelope. Formation of cleavage furrow. 4 haploid daughter cells with monad chromosomes (1 chromatid). In 2n=24, how many chromosomes for each daughter cell? Homologous chromosomes? chromatids?  Check your understanding! From the Anaphase II you created: 1. Model the Telophase II and Cytokinesis for 2n=4. GAMETOGENESIS Spermatogenesis Oogenesis Comparison of Mitosis and Meiosis  CONCEPT CHECK For each daughter cell at the end of Meiosis I and Meiosis II in human sex cells (2n=46), 1. How many chromosomes are present? 2. How many sister chromatids are present? 3. How many homologous pairs are present?  CONCEPT CHECK How many sets of chromosomes are present in each of the following cell types (human), 1. An oogonium? 2. A primary spermatocyte? 3. A spermatid? 4. A cell during anaphase I? Anaphase II? 5. A secondary oocyte? 6. A polar body from a primary oocyte?  CONCEPT CHECK Suppose there are 100 spermatogonium present, how many of the ff will be produced? 1. Primary spermatocyte? 2. Secondary spermatocyte? 3. Spermatids?  CONCEPT CHECK Suppose there are 100 oogonium present, how many of the ff will be produced? 1. Primary oocyte? 2. Secondary oocyte? 3. First polar bodies? 4. Second polar bodies? CONCEPT CHECK  CONCEPT CHECK If a certain spermatogonium have 2n=12, what is the probability of a sperm cell having equal amounts of maternal and paternal chromosomes to fertilize an egg cell? Edited* and Prepared by: Reviewed by: JERICK A. VIZ JERILE MAE E. CASIMIRO SST-II SST-III / AUH, Biology Date: September 9, 2024 Date: * Edited from Biology 2 PPT from Casimiro and Viz (2023)