Ro_Lecture2 - Mitosis and Meiosis Traits are controlled by...

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1 Mitosis and Meiosis Traits are controlled by genes Each individual contains two copies of a gene. Gene segregation Independent assortment What is the biological basis for Mendel’s laws? green x yellow green x green green: green:green:yellow
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2 Genes reside on Chromosomes Because genes reside on chromosomes, understanding the behavior and inheritance patterns of individual genes requires an understanding of the behavior of inheritance patterns of chromosomes. The processes of mitosis and meiosis describe the two basic patterns of chromosome behavior in higher eukaryotes Mitosis: a form of cell division that produces two daughter cells of identical genotypes Involves replication and segregation Meiosis: a form of cell division that produces four haploid products from the original diploid parental cell. Meiosis only occurs in a small specialized set of cells known as the germ cells.
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3 Mitosis 2N ----> 2N+2N Meiosis 2N ---->N+N+N+N
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4 The Mitotic cell cycle The mitotic cycle alternates between the replication of each chromosome (S phase) and the segregation of the replicated chromosomes to two daughter nuclei (M phase). The intervals between these phases are known as gap phases and this divides the cell cycle into four phases M, G1, S and G2. Interphase consists of G1, S, and G2.
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5 A a B b Smallest number: The female of a subspecies of the ant, Myrmecia pilosula, has one pair of chromosomes per cell. Its male has only one chromosome in each cell. Largest number: In the fern family of plants, the species Ophioglossum reticulatum has about 630 pairs of chromosomes, or 1260 chromosomes per cell. Species Diploid number Human 46 Monkey 42 Dog 78 Cat 38 Mouse 40 Frog 26 Fruitfly 8 C. Elegans Corn 20 S. Cerevisiae 32 S. Pombe 6 n=2 Homologous Chromosomes (99.99% similar) “n” refers to the number of chromosomes in a haploid Diploids are 2N
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6 Mitosis Mitosis is the period in which the chromosomes condense align along the metaphase plate and migrate to opposite poles. In part because this is the most visibly dramatic stage in the cell cycle much research has focused on these mitotic events. Net result: The creation of two daughter cells with identical chromosome complements.
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7 Replication of DNA Each DNA mol is a chromatid The two chromatids attached to the centromere are called sister chromatids A a B b A A a a b b B B A a B b A a B b A A a a b b B B No pairing of homologous Chromosomes Sister chromatids separate to opposite poles Homologous Chromosomes 99.99% identical
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8 Cell cycle and cancer Currently the cell cycle and mitosis are among the most intensively investigated areas of research. This is primarily due to the fact that: 1. That structural and regulatory components governing the cell cycle are conserved throughout the phyla. That is, the same proteins are used in yeast, flies and humans. 2. A number of the mutations that produce cancer in humans
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This note was uploaded on 04/15/2008 for the course BIO 105 taught by Professor Sullivan during the Fall '08 term at University of California, Santa Cruz.

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Ro_Lecture2 - Mitosis and Meiosis Traits are controlled by...

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