lecture 7

lecture 7 - Lecture #7- Polygenes and Multifactorial...

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Lecture #7- Polygenes and Multifactorial Inheritance (ch 5, p 94-115; chapter 18, p 427- 428) I. Polygenic (quantitative) Inheritance: when more than one gene contributes to a phenotype. A. Mendelian vs Polygenic Traits (figure 5.2) Mendelian traits F1 show one of the parental traits F2 phenotypes are distinct = discontinuous variation Polygenic traits F1 show a phenotype intermediate to that of the parents. F2 show a range of continuously varying phenotypes -Corresponds to a bell-shaped curve in a population Characteristics of Polygenic Inheritance -Quantitative: measured using a scale of numbers -Phenotypes vary over a wide range -Use populations B. The Additive Model for Polygenic Inheritance (Handout) -Trait is controlled by several genes; each of each has two alleles -Involves incomplete dominance -Each dominant allele makes an equal additive contribution (AA contributes twice that of Aa) -Genes are located on separate chromosomes -Increase of number of genes involves -> increase in number of phenotypic classes (fig. 5.5.) II. Multifactorial Traits: Interaction between a gene (Multifactorial Mendelian) or genes (Multifactorial Polygenic) with the Environment leads to the phenotype. A. Mendelian and Polygenic Multifactorial traits:
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lecture 7 - Lecture #7- Polygenes and Multifactorial...

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