Bio 132 Exam 2 Objectives

Bio 132 Exam 2 Objectives - 9.5 Explain the significance of...

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Explain the significance of mitosis, and describe the process. In mitosis, identical chromosomes are distributed to each pole of the cell, and a nuclear envelope forms around each set. During Prophase , duplicated chromosomes, each composed of a pair of sister chromatids, become visible with the microscope. The nucleolus disappears, the nuclear envelope breaks down, and the mitotic spindle begins to form. During Metaphase , the chromosomes are aligned on the metaphase plate of the cell; the mitotic spindle is complete and the kinetochores of the sister chromatids are attached by microtubules to opposite poles of the cell. During Anaphase , the sister chromatids separate and move to opposite poles. Each former chromatid is now a chromosome. During Telophase , a nuclear envelope re-forms around each set of chromosomes, nucleoli become apparent, the chromosomes uncoil, and the spindle disappears. Cytokinesis generally begins in telophase. 9.6 Differentiate between asexual and sexual reproduction. Offspring produces by asexual reproduction usually have hereditary traits identical to those of the single parent. Mitosis is the basis for asexual reproduction in eukaryotic organisms. In sexual reproduction , two haploid cells, or gametes , fuse to form a single diploid zygote . In a sexual life cycle, meiosis must occur before gametes can be produced. 9.8 Explain the significance of meiosis, and diagram the process. A diploid cell undergoing meiosis completes two successive cell divisions, yielding four haploid cells. Meiosis I begins with prophase I , in which the members of a homologous pair of chromosomes physically join by the process of synapsis . Crossing-over is a process of genetic recombination during which homologous (nonsister) chromatids exchange segments of DNA strands. At metaphase I , tetrads - each consisting of a pair of homologous chromosomes held together by one or more chiasmata - line up on the metaphase plate . The members of each pair of homologous chromosomes separate during meiotic anaphase I and are distributed to different nuclei. Each nucleus contains the haploid number of chromosomes; each chromosome consists of two chromatids. During meiosis II , the two chromatids of each chromosome separate, and one is distributed to each daughter cell. Each former chromatid is now a chromosome. 9.9 Contrast mitosis and meiosis, emphasizing the different outcomes. Mitosis involves a single nuclear division in which the two daughter cells formed are genetically identical to each other and to the original cell. Synapsis of homologous chromosomes does not occur during mitosis. Meiosis involves two successive nuclear divisions and forms four haploid cells. Synapsis of homologous chromosomes occurs during prophase I of meiosis.
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Bio 132 Exam 2 Objectives - 9.5 Explain the significance of...

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