Chap7 - CELLULAR REPRODUCTION Chapter 7 Cell Cycle Reproduction Essentials of Cellular Reproduction • hereditary information that directs life

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Unformatted text preview: CELLULAR REPRODUCTION Chapter 7 Cell Cycle - Reproduction Essentials of Cellular Reproduction • hereditary information that directs life processes is passed from parent to offspring • materials in the cytoplasm that the offspring need to survive is also passed on from parent Different Life Cycles Use Different Modes of Cell Reproduction • The lifespan of an organism is linked to cell reproduction — usually called cell division . • Organisms have two basic strategies for reproducing themselves: • Asexual reproduction • Sexual reproduction • Cell division is also important in growth and repair of tissues. Overview of Cell Division Mechanisms • Individual cells or organisms produce offspring by the process of reproduction • When a cell reproduces, each descendent receives information coded in DNA, and enough cytoplasm to begin operating Different Life Cycles Use Different Modes of Cell Reproduction • In asexual reproduction the offspring are clones —genetically identical to the parent. • Any genetic variations are due to mutations . • A unicellular prokaryote may reproduce itself by binary fission. • Single-cell eukaryotes can reproduce by mitosis. • Other eukaryotes are also able to Asexual Reproduction on a Large Scale • Sexual reproduction requires gametes —two parents each contribute one gamete to an offspring. • Gametes form by meiosis —a process of cell division. • Gametes—and offspring—differ genetically from each other and from the parents. • DNA in eukaryotic cells is organized into chromosomes . • A chromosome consists of a single molecule of DNA and proteins. • Somatic cells —body cells not specialized for reproduction • Each somatic cell contains two sets of chromosomes (homologs) that occur in homologous pairs . • Gametes contain only one set of chromosomes—one homolog from each pair. • Haploid cell—Number of chromosomes = n • Fertilization —Two haploid gametes (female egg and male sperm) fuse to form a zygote . • Chromosome number in zygote = 2 n and cells are diploid . Different Life Cycles Use Different Modes of Cell Reproduction • All kinds of sexual life cycles involve meiosis: • Haplontic life cycle—in protists, fungi, and some algae—zygote is only diploid stage • After zygote forms it undergoes meiosis to form haploid spores , which germinate to form a new organism. • Organism is haploid, and produces gametes by mitosis—cells fuse to form diploid zygote. All Sexual Life Cycles Involve Fertilization and Meiosis (Part 1) Different Life Cycles Use Different Modes of Cell Reproduction • Alternation of generations —most plants, some protists; meiosis gives rise to haploid spores • Spores divide by mitosis to form the haploid generation ( gametophyte )....
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This note was uploaded on 01/09/2012 for the course BIO 160 taught by Professor Howardhaemmerle during the Winter '12 term at Bellevue College.

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Chap7 - CELLULAR REPRODUCTION Chapter 7 Cell Cycle Reproduction Essentials of Cellular Reproduction • hereditary information that directs life

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