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Unformatted text preview: BIOLOGY 1002 Chs. 10-14 Study Guide Ch. 10 Meiosis Fertilization of two haploid nuclei produces diploid nucleus in the zygote Results of Mitosis: 2 diploid cells; each identical to parent Results of Meiosis: 4 haploid cells; differ from parent & one another Asexual Reproduction: one parent produces offspring and each inherits the same # and kinds of genes as its parent (which means asexually produced offspring can only be clones) Sexual reproduction involves meiosis, gamete formation, & fertilization In sexual reproduction the first cell of a new individual ends up w/ pairs of genes on pairs of homologous chromosomes (one is maternal the other is paternal) Allele: one or two or more molecular forms of a gene that arise by mutation and code for different versions of the same trait (these lead to variations in physical appearance & behavioral traits) First step in sexual reproduction: meiosis (type of nuclear division that reduces the parental chromosome number by half to form gametes) Gamete: haploid cell formed by meiotic cell division of a germ cell (required for reproduction) ex: eggs and sperms Meiosis IS similar to mitosis Before cell proceeds from interphase to mitosis or meiosis is duplicates DNA Each duplicated chromosome consists of 2 sister chromatids linked at the centromere In both mitosis and meiosis, microtubules of the spindle apparatus move the chromosomes in prescribed directions Differences in meiosis and mitosis: mitosis involves single nuclear division & meiosis requires two consecutive divisions (meiosis I and meiosis II) & mitosis maintains the chromosome # whereas meiosis halves it When diploid cell undergoes meiosis: moves through 8 stages and produces haploid cells (4) Meiosis forms gametes (like sperm & eggs) Meiosis I: Prophase I, Metaphase I, Anaphase I, Telophase I Meiosis II: Prophase II, Metaphase II, Anaphase II, Telophase II Remember chromosomes duplicated before meiosis began! Genetic variation is enhanced in 2 ways: crossing over (occurs during prophase I) & each crossover represents a chance to swap alleles & the 2 nd results from the random alignment of chromosomes at metaphase I Gametes form by spermatogenesis in male animals (forms 4 haploid spermatids) each develops into a mature sperm cell Gametes form by oogenesis in female animals (cytoplasmic divisions are unequal) thus giving rise to one mature egg (ovum) & three smaller polar bodies which degenerate so the female germ cell produces only ONE functional gamete Ch. 11 Observable Patterns of Inheritance Ch....
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- Spring '06