BIO 111 Chapter Notes - Chapter 7.4, 8.2-8.4: Homologous Chromosome, Nondisjunction, Mendelian Inheritance
Document Summary
7. 4: meiosis halves the nuclear chromosome content and generates diversity. Genetic diversity caused by crossing over and independent assortment: crossing over the four chromatids in each homologous chromosome creates a tetrad through a process called synapsis. This creates chiasmata (cross over between non-sister chromatids) At chiasma, genetic material is exchanged between no-sister chromatids through a process called crossing over. Crossing over causes recombinant chromatids that have genetic information from both mother and father. Depending on how the homologous pairs line up at metaphase 1, anaphase will pull to each pole a certain amount of maternal chromosomes and parental chromosomes. Meiotic errors lead to abnormal chromosome structures and numbers: nondisjunction failure of homologous chromosome pair separations or chromatid separation. If nondisjunction occurs at anaphase 1, then all gametes are wrong because none have the right amount of chromosomes (either have too many or too few) If nondisjunction occurs at anaphase 2, only two gametes are affected.
