BIOL 240 1st Edition Lecture 2 Outline of Last Lecture I. Chromosomes1. Designations2. Diploid cellsII. Cell Cycle1. Mitosis2. Overview of MeiosisOutline of Current Lecture I. Meiosis III. Meiosis IIIII. SpermatogenesisIV. OogenesisCurrent LectureI. Meiosis I1. Metaphase I: paired homologs align on the spindle centromeres facing opposite poles2. Anaphase I: sister chromatids still connected at their centromeres segregate to opposite poles; crossovers are regulated so that at least one occurs3. Telophase I: chromosomes reach opposite poles and cytokinesis begins to occur4. Prophase I: two haploid cells are producedII. Meiosis II (much like mitosis)1. Metaphase II: after Prophase I, centromeres align on the metaphase plate2. Anaphase II: sister chromatids are segregated to opposite poles3. Telophase II: chromosomes reach opposite poles and cytokinesis occurs; the products are 4 haploid gametes that are all genetically different due to homolog segregation and crossing-overIII. Spermatogenesis (production of male gametes)In male animal cells, cells derived from germ cells are called spermatogonium. Males have these cells up until the point when maturation (puberty) begins. Once this happens, the spermatogonium grow into primary spermatocyte, which undergoes the first division of meiosis. The products are two secondary spermatocytes, each containing a haploid number of dyads. Both These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.of these then undergo the second meiotic division, producing a total of four (two from each) spermatids. Spermatids then undergo physical changes and form intospermatozoa, which is what is needed to fertilize a female gamete.IV. Oogenesis (production of female gametes)In female animal cells, cells called oogonium form into primary oocytes, all of which are produced before birth. Once puberty is reached, the primary oocytes undergo the first meiotic division, products being a secondary oocyte and the first polar body. The secondary oocyte is what will go on to be fertilized, so it contains most of the cytoplasm in hopes of nourishing an embryo. The first polar body is discarded. Upon fertilization, the second meiotic division occurs and the secondary oocyte divides into an ootid and a second polar body. The ootid reforms into an ovum and the second polar body is also
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