Lecture5_2012_illustrations

Lecture5_2012_illustrations - Modifications of Mendelian...

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Modifications of Mendelian ratios part II
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Recap from Thur. X-linked traits Imprinted traits Non-nuclear traits: Mitochondrial Maternal effect Penetrance and expressivity
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Recap from Thur. X-linked traits Imprinted traits Non-nuclear traits: Mitochondrial Maternal effect Penetrance and expressivity
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Modification of Mendelian ratios Mendel’s postulates • genes operate in pairs • alleles are either dominant or recessive • Alleles segregate randomly • each parent gives 1 allele to its progeny • Genes sort independently (independent assortment) • (1 gene: 1 phenotype) Cases which cause deviations from mendelian ratios and in some cases exceptions or additions to Mendel’s postulates
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Topics covered in Thurs. Lecture • Incomplete Dominance • Alleles which when combined display a partial or blended phenotype of the phenotypes seen in each allele separately (new phenotype) • Heterozygotes display an intermediate phenotype (between wt and mutant alleles) • Co-dominance • Alleles which when combined display the phenotype of each separate allele simultaneously (combined phenotype, not new) • Heterozygote displays both phenotypes, simultaneously
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• Epistasis • More than >1 gene is involved in a single trait • Pleiotropy • 1 gene/allele can give many traits • Lethal alleles • An allele causes death prior to observation, altering ratio of traits observed • Indicates an essential gene • Mendelian ratios can be observed if observation is conducted early enough Topics covered in Thurs. Lecture
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Topics covered in Thurs. Lecture • Changes to Mendel’s postulate of dominant and recessive genes • Incomplete Dominance • Co-dominance • Changes to Mendel’s postulate of 1 gene - 1 phenotype • Epistasis and Pleiotropy • Changes to Mendelian ratios due to nature of allele • Lethal alleles
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Recap from Thur. X-linked traits Imprinted traits Non-nuclear traits: Mitochondrial Maternal effect Penetrance and expressivity Mendel’s postulates • genes operate in pairs • alleles are either dominant or recessive • Alleles segregate randomly • each parent gives 1 allele to its progeny • Genes sort independently (independent assortment) • (1 gene: 1 phenotype) Modification of Mendelian ratios
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Question: This pedigree of the British royal family traces individuals affected by hemophilia. What is unique about the affected individuals? What is the mode of inheritance?
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Question: This pedigree of the British royal family traces individuals affected by hemophilia. What is unique about the affected individuals? What is the mode of inheritance? - Only males are affected - X-linked recessive
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- Only males are affected - X-linked recessive
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- Only males are affected - X-linked recessive
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Discovery of X-linked traits using fly eye color
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Discovery of X-linked traits using fly eye color
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Discovery of X-linked traits using fly eye color
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Discovery of X-linked traits using fly eye color Females: wt Males: mut Females: 25% wt, 25% mut Males: 25% wt, 25% mut
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Lecture5_2012_illustrations - Modifications of Mendelian...

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