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section6.1.notebook November 14, 2013 You have two types of cells in your body: somatic cells, and germ cells. Somatic cells are your body cells. They undergo mitosis when they need to divide. Germ cells are your reproductive cells also referred to as gametes. male gametes are called sperm cells female gametes are called egg cells. Sexual reproduction involves the fusion of two gametes that results in offspring that are a genetic mixture of both parents. 1 section6.1.notebook November 14, 2013 Gametogenesis the production of gametes. Sperm cells (male gamete) smaller than female gamete contribution to the embryo is DNA must be able to swim, modifications are made to the cell for this to happen. Egg cells (female gamete) gives DNA, contributes organelles, molecular building blocks, and other materials for a successful embryo to develop 2 section6.1.notebook November 14, 2013 Fertilization the actual fusion of two gametes. Occurs when the sperm fertilizes the egg. A zygote is formed that will have the number of chromosomes in a diploid cell. Develops by mitosis into a multicellular organism. Diploid a cell with 2 copies of each chromosome, (2n) number of chromosomes, body cells are diploid. one from female parent one from male parent Haploid gametes that contain only one of each kind of chromosome (n) number of chromosomes. 3 section6.1.notebook November 14, 2013 Each organism has a specific amount of chromosomes in their cells. The number of chromosomes is not related to the complexity of an organism. Examples: Adder's Tongue Fern 1260(2n) 630(n) Fruit Fly 8(2n) 4(n) Humans 46(2n) 23(n) Autosomes chromosomes that contain genes for characteristics not directly related to the sex of an organism. Chromosome pairs 122 are autosomes Sex Chromosomes ones that control the development of sexual characteristics. Very different from one another. X and Y are standard XX indicates female, XY indicates male Chromosome pair 23. 4 section6.1.notebook November 14, 2013 Human cells have 46 chromosomes. If cells only reproduced through mitosis then when an egg cell and a sperm cell fuse, the new cell would have 92 chromosomes! Meiosis is the type of cell division that produces gametes with half the number of chromosomes as a parent's body cells. Two separate divisions occur (Meiosis I and II) Begins with 1 diploid (2n) cell, and results in 4 haploid (n) cells. 5 section6.1.notebook November 14, 2013 Homologous chromosomes two chromosomes (one from mom and one from dad) that have the same length and same general appearance. contain the same genes in the same order. 6 section6.1.notebook November 14, 2013 Can you identify Homologous Chromosomes? The diagram below shows chromosomes 1 with four different genes present. These genes are represented by the letters F, g, h, and J. Possible homologous chromosomes of chromosome 1 are labeled 2 5. Examine the five chromosomes and the genes they contain to determine which of chromosomes 25 are homologous with chromosome 1. 7 section6.1.notebook November 14, 2013 1. Could chromosome 2 be homologous with chromosome 1? Explain. yes, because the genes are in the same location and position 2. Could chromosomes 4 be homologous with chromosome 1? Explain. no, because the last gene is not the same 3. Could chromsome 4 be homologous with chromosome 1? Explain. no, because they have completely different genes 4. Could chromosome 5 be homologous with chromosome 1? Explain yes, same as #1 8