Lecture_twentyone - I. The Role of Cell Division in...

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I. The Role of Cell Division in Asexual/Sexual Life Cycles A. Asexual reproduction is based on mitotic division of the nucleus. It may be a unicellular organism reproducing itself, or: Cells of multicellular organisms that break off to form a new individual The offspring are clones —genetically identical to the parent.
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Fungus
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A. Sexual reproduction : the offspring are not identical to the parents. Meiosis produces gametes that differ genetically from the parents, and also from each other. This is really the mechanism that drives evolution
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Remember Somatic cells —body cells not specialized for reproduction. Each somatic cell contains homologous pairs of chromosomes with corresponding genes. Each parent contributes one homolog .
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Gametes contain only one set of chromosomes. Haploid : number of chromosomes = n Fertilization : two haploid gametes (female egg and male sperm) fuse to form a diploid zygote ; chromosome number = 2 n Diploid cell Haploid cell s
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There are several kinds of sexual life cycles: Haplontic life cycle : protists and many fungi; zygote is the only diploid stage.
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Lecture_twentyone - I. The Role of Cell Division in...

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