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Chapter 10 Notes (Summer2011)

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Biological Sciences
Rosada Silva

BIOB11Summer2011 Chapter 10 The Nature of the Gene and the Genome The Concept of a Gene o Hereditary factors consist of DNA and reside on chromosomes o The collective body of genetic information in an organism is called the genome o The study of genetics began with the concept of the gene as a unit of inheritance o These days the concepts of inheritance and gene transmission are considered factsallows us to forget how radical the concept was o While breeding pea plants Gregor Mendel developed the principles on inheritance before anyone even knew what a gene washis work became the foundation for the science of genetics o He controlled fertilization put pollen on paintbrush and self fertilized or cross fertilized pea plants o He observed plants and their offspring for 2 years as they self fertilizeddiscovered 7 traits that bred true o Before Mendel people believed that traits in offspring resulted from a blending of the traits of each parentMendel showed that when two parents with different varieties of a trait bred the offspring would look like one or the otherexample wrinkled seeds x round seeds did not produced semiround or semiwrinkled seeds butround seeds o Mendel called the expressed parental trait the dominant trait o Two purebreeding parents P1 and P2 gave an F1 filial generation that looked like the dominant parentthe F1 generation was uniform they all looked the same o To find out if the F1 generation posses non dominant traits in some hidden way Mendel self fertilized the F1 generation o When F1 round x F1 roundF2 round or wrinkledF2 round was consistently 3x more frequent than wrinkled because it is the dominant trait o 1 The characteristics of organisms are governed by units of inheritance called geneso Each trait is controlled by 2 forms of a gene called alleles o Alleles can be identical or non identicalo When alleles are non identical the dominant allele masks the recessive allele o 2 A reproductive cell gamete contains one gene of each trait o Somatic cells arise by the union of male and female gametes o Two alleles controlling each trait are inheritedone from each parent o 3 The pairs of genes are separated segregated during gamete formation o 4 Genes controlling different traits segregate independently of one anotherindependent assortmentexample tall plants are not always going to be yellow or round o Mendel presented his work in 1866 but is was unused until 1900 o Mendels work didnt address the physical nature of geneso During this time biologists were studying the physical basis of heredity Physical Carriers of Genes o Wherever physical units of heredity came from they had to be passed on from cell to cell be passed from generation to generation and must be contained within a single cell o The cytoplasm and its contents divided randomly between daughter cells o Nuclear contents divided equally 1
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