Chapter_14_Outline - Chapter 14- Mendel and the Gene Idea...

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Chapter 14- Mendel and the Gene Idea I. Gregor Mendel’s Discoveries 1) The favored model of heredity in the nineteenth century prior to Gregor Mendel was the “blending” hypothesis, the idea that genetic material contributed by the two parents mixes in a manner analogous to the way blue and yellow paints blend to make green. 3) Mendel’s methods had various features that contributed to his success, such as the availability of peas in many varieties (i.e. purple and white flowers). Also, the use of peas gave Mendel strict control over which plants mated with which. Furthermore, Mendel made sure he started his experiments with varieties that were true-breeding (offspring were of same variety). 4) true-breeding- plants that produce offspring of the same variety when they self-pollinate. hybridization- the mating (crossing) of two varieties. monohybrid cross- an organism that is heterozygous with respect to a single gene of interest. P generation- the parent individuals from which offspring are derived in studies of inheritance. F 1 generation- the first filial (hybrid) offspring in a genetic cross-fertilization. F 2 generation- offspring resulting from interbreeding of the hybrid F 1 generation. 5) Mendel’s hypothesis that led him to deduce the law of segregation: Alternative versions of genes (different alleles) account for variations in inherited characters. [Gene for flower color has two versions: purple and white.] For each character, an organism inherits two alleles, one from each parent. [Hybrids inherited purple-flower allele from one parent and white-flower allele from the other.] If the two alleles differ, then one, the dominant allele, is fully expressed in the organism’s appearance; the other, the recessive allele, has no noticeable effect on the organism’s appearance. [The F 1 plants had purple flowers because the allele for purple is dominant and white recessive.] The two alleles for each character segregate (separate) during gamete production. [Ovum and sperm each has one of the two alleles present in the somatic cells of organism- distribution of homologous chromosomes to different gametes in meiosis.] 8) Organisms that are heterozygous for a specific gene have two different alleles for that gene; they are homozygous if they have a pair of identical alleles for this gene. Genotype is the genetic makeup of an organism, while the phenotype is the organism’s traits. 9)
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This note was uploaded on 06/15/2010 for the course FDST 4080 taught by Professor Pegg during the Spring '10 term at University of Georgia Athens.

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Chapter_14_Outline - Chapter 14- Mendel and the Gene Idea...

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