Chapter 9 Notes - Chapter 9 Patterns of Inheritance 9.1 The...

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Chapter 9: Patterns of Inheritance9.1 The study of genetics has ancient rootsAncient Greek physician HippocratesoParticles called “pangenes” travel from each part of the body to the eggs or spermand then are passed to the next generationoChanges that occur in the body during an individual’s life are passed on this wayHippocrates was incorrectoReproductive cells are not composed of particles from body (somatic) cellsoChanges in somatic cells do not influence gametes 19thcentury: observing inheritance patterns in plants, biologists establish offspring inherittraits from both parentso“Blending hypothesis:” hereditary materials contributed by the male and female parents mix in forming the offspring similar to the way blue and yellow paint make green plantoEventually rejected become it does not explain how traits that disappear in one generation can reappear in later ones (dominate and recessive traits)9.2 The science of genetics began in an abbey gardenHeredity: transmission of traits from one generation to the nextGenetics: scientific study of heredityGregor Mendel oAugustinian monk in 1860soBreeding garden peasShort generation timesLarge number of offspringCan control mating: self fertilization oCorrectly argued parents pass discrete “heritable factors” on to their offspringoHeritable factors, today called genes, retain their individuality generation after generationGenes may be sorted but each gene permanently retains its identity oTrue breeding varieties: varieties for which self fertilization produced offspring all identical to the parentoCross breeding Hybrids: offspring of two different varietiesHybridization: cross fertilizationP generation: true breeding parentF (1) generation: hybrid offspringF (2): offspring of F1 generationoSuccess was due to his experimental approach and choice of organism and to his selection of characters to study Character: heritable feature that varies among individualsTrait: each variant for a character9.3 Mendel’s law of segregation describes the inheritance of a single characterMonohybrding cross: follows just one characterFour hypothesis:
oThere are alternative versions of genes that account for variations inherited characteristics.Alternative versions of a gene are called alleles oFor each character, an organism inherits two alleles, one from each parent. Homozygous: identical alleles Heterozygous: two different alleles oIf the two alleles of an inherited pair differ then one determines the organism’s appearance and its called the dominant allele, the other has no noticeable effect on the organisms’ appearance and is called the recessive allele.

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