Genetics Notes - Genetics Notes 01/30/09 The theory of...

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Genetics Notes 01/30/09 The theory of particulate inheritance hypothesizes that inheritance is produced by discrete particles. Alternative forms of these particles account for the genetic variations in inherited characteristics. Each particle controls one and only one characteristic. (This tenant is falsified by most loci controlling more than one trait in an organism) Pleitropy. Therefore, they are not on structures like chromosomes. (No strings that hold the particle together) The particles assort into the gametes according to two principles we call Mendel’s laws. (1. Equal segregation 2. Independent Assortment) Students should know all boldface terms for each chapter unless told otherwise. Mendel’s laws: Equal segregation and Independent assortment. Homologous chromosomes have the same loci. The probability of an event is defined to be the number of ways an event occurs divided by the total number of possible outcomes. While these “laws” are still at times able to make accurate predictions concerning inheritance, they have both been falsified. Linkage falsifies independent assortment. Monohybrid and dihybrid crosses Mono- one locus (Aa x Aa) di- two loci (AaBb x AaBb) The probability of two independent events co-occuring in the same time is equal to the product of their probabilities. “And” = product rule “Or” = sum rule. Test cross- we take an individual with a dominant phenotype and cross with a homozygous recessive one. Systems of sex determination – we break them in to two large categories Chromosomlly determined – XY system in fruit flies The absence of the second X makes it a male. The Y chromosome has the loci to make the male fertile
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One observation congruent of the hypothesis that genes are on the chromosomes is that the Y chromosome confers fertility to the Y chromosome and therefore it must have the loci for fertility. In mammals, XO is a female disorder, Turner Syndrome. Syndrome- is a collection of symptoms Female is the homogametic sex Male is the heterogametic sex X has a lot more genes on it than the Y. Second chromosomlly is determined by the WZ system. WZ is female w - w - is male Moths and butterflies, and birds have this system Sex linked if its one of the two chromosomes that determines the sex. X-linked or Y- linked are the subsets of sex linked. Chromosomes other than the sex chromosomes involved in sex determination are called autosomes. Pedigree analysis. Know symbols for pedigree analysis; page 66 Fig 2-28. For this course we consider 4 modes of inheritance- autosomal recessive, autosomal dominant, x-linked dominant and x-linked recessive, and cytoplasmic (or maternal) 02/02/09 Fig 2-25. Pseudoautosomalregion.
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This note was uploaded on 11/11/2010 for the course BIO 325 taught by Professor Saxena during the Spring '08 term at University of Texas at Austin.

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Genetics Notes - Genetics Notes 01/30/09 The theory of...

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