Genetics380_Oct132009_3slides

Genetics380_Oct132009_3slides - Genetics 380 Part II Oct 13...

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1 Genetics 380 Part II • Oct 13 and Oct 15: Human genetics and pedigree analysis (Chap. 6) • Oct 20: Gene mapping: genetic and molecular approaches (Chap. 7, 19) • Oct 22 and Oct 27: DNA: replication, repair, and mutation (Chaps. 10, 12, 18) • Oct 29 and Nov 3: RNA: Transcription and processing (Chaps 13, 14) • Nov 5 and 10: Protein: The genetic code & translation (Chap 15) • Nov 12: EXAM II Genetics 380 Human Genetics and Pedigree Analysis Reading: Chapter 6 of textbook. Human pedigree analysis • Human matings, like those of experimental model organisms, provide many examples of single-gene inheritance Pedigree analysis : scrutiny of medical records and matings Proband or propositus : the member of a family who first comes to the attention of the geneticist • Investigator traces the history of the phenotype through the history of the family, and draws a family tree, or pedigree, using standard symbols
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2 Autosomal recessive disorders Aa Aa A- A- aa aa Does this pedigree support the hypothesis of X-linked inheritance? Why or why not? Mendelian ratio?
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3 aa aa Aa Aa A- Aa A- Aa Aa A- A- A- A- Aa AA AA Deducing the genotypes Message In human pedigrees, an autosomal recessive disorder is generally revealed by the appearance of the disorder in the male and female progeny of unaffected parents.
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4 Autosomal dominant disorders Normal allele is recessive, defective allele is dominant. Pseudoachondroplasia phenotype (Dd or DD): abnormal long bone d’ment
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5 Polydactyly Dominant Piebald Spotting caused by mutation in c-kit Late onset of Huntington disease
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6 Message Pedigrees of Mendelian autosomal dominant disorders show affected males and females in each generation; they also show affected men and woman transmitting the condition to equal proportions of their sons and daughters. Autosomal polymorphisms In natural populations of organisms, a polymorphism is the coexistence of two or more common phenotypes of a character. The alternative phenotypes of a polymorphism (morphs) are often inherited as alleles of a single autosomal gene in the standard Mendelian manner. Human dimorphisms: Brown vs. blue eyes, pigmented vs. blonde hair, chin dimples vs. none, widow’s peak vs. none, attached vs. free earlobes Taste of chemical phenylthiocarbamide (PTC): foul or no taste Inheritance of a dimorphism: Pedigree for the ability to taste PTC
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7 Inheritance of a dimorphism: Pedigree for the ability to taste PTC tt tt tt tt tt tt tt tt tt tt tt Inheritance of a dimorphism: Pedigree for the ability to taste PTC tt tt tt tt tt tt tt tt tt tt tt T t T t T t T t T t T t T t Inheritance of a dimorphism: Pedigree for the ability to taste PTC tt tt tt tt tt tt tt tt tt tt tt T t T t T t T t T t T t T t T - T T - T - TT T t T T T
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8 X-linked recessive disorders Features: 1. More males than females affected 2. None of offspring of an affected male
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Genetics380_Oct132009_3slides - Genetics 380 Part II Oct 13...

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