CHAPTER 13 MEIOSIS AND SEXUAL LIFE CYCLES

CHAPTER 13 MEIOSIS AND SEXUAL LIFE CYCLES - CHAPTER 13...

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CHAPTER 13 MEIOSIS AND SEXUAL LIFE CYCLES Reproduction is an emergent property associated with life. The fact that organisms reproduce their own kind is a consequence of heredity. Heredity = Continuity of biological traits from one generation to the next - Results from the transmission of hereditary units, or genes, from parents to offspring. - Because they share similar genes, offspring more closely resemble their parents or close relatives than unrelated individuals of the same species. Variation = Inherited differences among individuals of the same species - Though offspring resemble their parents and siblings, they also diverge somewhat as a consequence of inherited differences among them. - The development of genetics in this century has increased our understanding about the mechanisms of variation and heredity. Genetics = The scientific study of heredity and hereditary variation. I. An Introduction to Heredity A. Offspring acquire genes from parents by inheriting chromosomes DNA = Type of nucleic acid that is a polymer of four different kinds of nucleotides. Genes = Units of hereditary information that are made of DNA and are located on chromosomes. - Have specific sequences of nucleotides, the monomers of DNA - Most genes program cells to synthesize specific proteins; the action of these proteins produce an organism's inherited traits. Inheritance is possible because: - DNA is precisely replicated producing copies of genes that can be passed along from parents to offspring. - Sperm and ova carrying each parent's genes are combined in the nucleus of the fertilized egg.
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The actual transmission of genes from parents to offspring depends on the behavior of chromosomes. Chromosomes = Organizational unit of heredity material in the nucleus of eukaryotic organisms - Consist of a single long DNA molecule (double helix) that is highly folded and coiled along with proteins - Contain genetic information arranged in a linear sequence - Contain hundreds or thousands of genes, each of which is a specific region of the DNA molecule, or locus Locus = Specific location on a chromosome that contains a gene - Each species has a characteristic number of chromosomes; humans have 46 (except for their reproductive cells). B. Like begets like, more or less: a comparison of asexual versus sexual reproduction Asexual Reproduction Sexual Reproduction Single individual is the sole parent. Two parents give rise to offspring. Single parent passes on all its genes to Each parent passes on half its genes, its offspring. to its offspring. Offspring are genetically identical to Offspring have a unique combination the parent. of genes inherited from both parents. Results in a clone, or genetically Results in greater genetic
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This note was uploaded on 03/18/2008 for the course BS 110 taught by Professor S.lawrence during the Spring '07 term at Michigan State University.

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CHAPTER 13 MEIOSIS AND SEXUAL LIFE CYCLES - CHAPTER 13...

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