HMB265 Final Exam notes

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University of Toronto St. George
Human Biology
Maria Papaconstantinou

HMB265H1 Final Exam Notes made by Man Lai HoLecture 2 Mendelian genetics for single gene traitsDiscrete simple genetics single gene traitsContinuous complex inheritanceSelffertilizationoQuick and easy to make purebreedinginbred lines genetically homogeneous lines that show same characteristics generation after generationBoth parents contribute hereditary material biparental inheritance2 copies of each trait in somatic cell Gametes contain one copy of the traitAlleles different forms of trait segregate randomlyInherited traits are dominant expressed in F1 hybrid and recessive silent in F1 hybridoDifference between genotype and phenotypeLaw of independent assortment different traits assort independentlyInheritance is particulate blending does not happenoHereditary factors do not modify each other in a permanent wayTest cross allows distinction between genotype and phenotypeoCross with homozygote recessiveDihybrid cross YyRr X YyRr normal ratios during independent assortmentoBasicsYYYyyyoYRX 916oYrrX 316oyyRX 316oyyrrX 116Lecture 3 Molecular basis of Genetic PolymorphismsAllelic differences at DNA level can influence mRNA expression andor protein function thus the phenotypeoDNAmRNAproteinorganismal traitsoEg SNP change in one AA disrupts activity of enzymeCodominance at DNA level GenotypeMutations source of allelic variationoPoint mutations SNPs Single nucleotide polymorphisms are allelesoInsertionsdeletionsoChanges in repeat numberoChromosomal rearrangementsGene expression with mutationoNull Alters proteinAt promoters exonsoLeaky somewhat alters proteinPartially on exonoSilent usually no alterationAt introns spliced outPKU Phenylketonuria Single gene disorderoNormal phenylalaninetyrosineoPKU phenylalaninephenylpyruvic acid malfunction in phehydroxylaseBuildup of phenylpyruvic acid interfere with nervous system developmentoMutations in both exons and introns interfere with splicing inactivate gene cause PKUHMB265H1 Final Exam Notes made by Man Lai HoBRCA1 geneoTumour suppressor genes important in repairing DNA damageoMutations in this gene interfere with DNA repair lead to cancer risk particularly breast and ovarian cancerHundreds of mutations found that increase riskHaplosufficency 50 of protein product is sufficient to give wild type phenotypeHaploinsufficiency 50 of protein product is insufficient to give wild type phenotypeDominant negative Mutant allele inhibits other allele from expressing normal amount ofproteinDetection of allelic polymorphism at molecular leveloPCR Amplification and DNA sequencingMost comprehensiveoSNP detectionOf 13 more common mutationsLecture 4 Mendelian Traits in Humans and Human pedigree analysisAutosomal inheritanceoLocated on non sex chromosomes 122oAutosomal dominantAa affected X aa unaffected affectedunaffected progenyAA and Aa exhibit affected phenotypeMales and females equally affected and may transmit traitAffected phenotype does not skip a generation trait tend to show up every genAffected children have at least one affected parentoAutosomal recessiveAa unaffected X Aa unaffected affectedunaffected progenyaa exhibit affected phenotypecan be children of two unaffected carriersMales and females equally affected and may transmit traitMay skip generationsoIf disease is rare assume outside individuals to be wild typeLecture 5 Extension to Mendelian Genetics Part 1Incomplete dominanceoIntermediate phenotype F1 hybrid distinct from either homozygous parentsoRR red RW pink WW whiteoPhenotypic ratios same as genotypic ratiosoEg Familial HypercholesteraemiaCodominanceoF1 hybrids express phenotype of both parents equallyoPhenotypic ratios same as genotypic ratiosGenes may have multiple alleles that segregate in populations oEg Blood typeA AOAAB BOBBAB AB
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