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Bio Study Guide

Bio Study Guide - I Chapter 9 Sexual Reproduction and...

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I. Chapter 9 – Sexual Reproduction and Meiosis A. Sexual reproduction involves the union of 2 sex cells, gametes, to form a single cell called a zygote B. Each chromosome in a body cell of a plant or animal normally has a partner chromosome C. The 2 partners are known as homologous chromosomes, are similar in shape, size, and the position of their centromeres D. The 46 chromosomes in the human cell have 23 homologous pairs E. If a cell contains 2 sets of chromosomes, it is called diploid and if it has only 1 set it is called haploid F. A division that reduces chromosome number is called meiosis i. Chromosome number is reduced by ½ ii. Involves 2 successive nuclear and cytoplasmic divisions, which produces up to 4 cells iii. Each of the 4 cells produced by meiosis contains the haploid number of chromosomes iv. The genetic information from both parents is shuffled so each haploid cell is unique v. 2 stages of meiosis, I and II 1. Each have prophase, metaphase, anaphase and telophase stages vi. Prophase I 1. The homologous chromosomes lie lengthwise side by side (Synapsis – fastening together) 2. Crossing over occurs only in Prophase I – a process in which paired homologous chromosomes exchange DNA 3. Crossing over produces new combinations of genes vii. Metaphase I 1. Tetrads line up on cell’s equator viii. Anaphase I 1. The paired homologous chromosomes separate and move toward opposite poles 2. Sister chromatids still remain attached at their centromeres ix. Telophase I 1. The chromatids de-condense, and cytokinesis occurs x. Prophase II 1. Chromosomes condense but the DNA does not replicate xi. Metaphase II 1. Chromosomes line up along the cells equator in groups xii. Anaphase II 1. Sister chromatids separate and chromosomes move to opposite poles xiii. Telophase II 1. Nuclei are formed at opposite poles of each cell and cytokinesis occurs G. Plants and fungi have some of the most complicated life cycles
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H. These life cycles, characterized by alternation of generation, consists of a multicellular diploid stage, sporophyte generation, and a multicellular haploid stage, gametophyte generation I. Sporophyte cells undergo meiosis to form haploid spores, each divides mitotically to produce a multicellular haploid gametophyte J. Female and male gametes fuse to form a diploid zygote that divides mitotically to form a multicellular diploid sporophyte K. Sporophyte Dominance – Ferns, conifers, flowering plants (Parts – roots, stems, leaves) II. Chapter 10 – The Basic Principles of Heredity A. Mendelian Genetics i. Recognized the existence of hybrids ii. Two Main Concepts of Inheritance 1. All hybrid plants that are the offspring of genetically pure parents are similar in appearance 2. When these hybrids mate with each other, they do not breed true, their offspring show a mixture of traits iii. Phenotype is the physical appearance of an organism iv. A true breeding line produces only offspring expressing the same phenotype v. Characters – the attributes for which heritable differences are known vi.
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Bio Study Guide - I Chapter 9 Sexual Reproduction and...

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