Lesson 30-31 Extensions of Mendelian Inheritance.ppt

Lesson 30-31 Extensions of Mendelian Inheritance.ppt - BIO...

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Unformatted text preview: BIO 325 Genetics Lectures 30 and 31 Extensions of Mendelian Inheritance When someone was boasting of having read many things, Castruccio said: It would be better to boast of having remembered them. Niccol Machiavelli, The Life of Castruccio Castracani of Lucca Inheritance patterns that obey the law of segregation and the law of independent assortment are classified as examples of Mendelian inheritance. Extensions of Mendelian Inheritance Inheritance patterns that obey the law of segregation and the law of independent assortment are classified as examples of Mendelian inheritance. Simple Mendelian inheritance indicates that two alleles are involved, and one is dominant over the other. Extensions of Mendelian Inheritance The prevalent alleles in a population are called wild-type alleles, which typically encode for normally expressed and functioning proteins. Different alleles of the same gene are called genetic polymorphisms . Inheritance Patterns of Single Genes Mutant alleles are those that have been changed by a mutation and are less common. Mutant alleles often have altered expression (typically decreased) or abnormal protein function. Inheritance Patterns of Single Genes Wild-type (dominant) allele Mutant (recessive) allele Purple flowers White flowers Axial flowers Terminal flowers Yellow seeds Green seeds Round seeds Wrinkled seeds Smooth pods Constricted pods Green pods Yellow pods Tall plants Dwarf plants Wild-type (dominant) allele Mutant (recessive) allele Red eyes White eyes Normal wings Miniature wings In many human genetic diseases, the recessive allele contains a mutation. This prevents the allele from producing a fully functional protein. Inheritance Patterns of Single Genes For an autosomal trait with a simple dominant/recessive relationship, the presence of a single recessive allele does not affect the phenotype of the heterozygote. Inheritance Patterns of Single Genes The dominant allele normally produces more protein than is needed. Therefore, the loss of protein production by the recessive allele is not enough to influence the phenotype. Inheritance Patterns of Single Genes Homozygous dominant individuals have an excess of protein, heterozygous individuals have adequate protein, and homozygous recessive individuals have a deficiency of protein. Inheritance Patterns of Single Genes Incomplete dominance is characterized by heterozygous individuals with a phenotype that is intermediate between the dominant and recessive phenotypes. Inheritance Patterns of Single Genes In the four oclock plant, Mirabilis jalapa, homozygous red-flowered plants that are crossed with homozygous white-flowered plants yield pink-flowered plants....
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Lesson 30-31 Extensions of Mendelian Inheritance.ppt - BIO...

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