genomeguide2 - random genome study guides

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Study guide for the second midterm exam, BME/BIO 80H, The Human Genome From lecture 6 Be able to recognize inheritance patterns as shown in pedigree charts X-link=females more often affected, affected males only passed to daughters, female heterozygous=pass to half of offspring, homozygous=pass to all offspring Y-link=only expressed in males, fathers pass to sons, all persons with allele affected Mitochondrial inheritance=mother passes trait to all children, father never passes Late onset inheritance (Huntington’s and Porphyria) testis determination factor (TDR/SRY)-determining maleness Huntington= degeneration of nervous system, no cure, death is 5-15yrs after onset, onset=30-50 Porphyria=disruption in ability to produce heme, onset middle age, environmental triggers Penetrance and Expressivity Penetrance=probability person with disease genotype will have disease (100% = all have it, 30% = 30% of people have it) Expressivity=range of variation within the phenotype of a trait From lecture 7 Definition, characteristics and expected inheritance patterns concerning polygenic traits Polygenetic inheritance=more than one gene contributes to phenotype The additive model for polygenic inheritance Controlled by several genes w 2 alleles, incomplete dominance, each dominant allele makes equal and additive contribution to phenotype (AA = 2x of Aa), recessive contributes nothing Definition and characteristics of multifactorial traits Multifactorial inheritance=involves interaction between genes and environment Single gene + environment = multifactorial mendelian trait Multiple genes + environment = multifactorial polygenic trait (alzheimers, cancer, heart disease, diabetes, schizophrenia, others) Multifactorial threshold traits Shows a discontinuous distribution, only persons w phenotype above certain threshold liability will develop the condition when exposed to certain environmental conditions, relative risk of inheritance decreases w/ each degree of separation, further separated=fewer genes in common Definition and calculation of heritability (include correlation coefficients) Correlation coefficient measures heretibility Identical twins = 1/1 = cc of 1.0 (100%) Parent – child = ½ = cc of 0.5 (50%) Siblings = ½ = cc of 0.5 (50%) Grandparents – grandchildren = ¼ cc of 0.25 (25%) Observed cc/expected cc (observed over expected) = heritability Biology of twins Monozygotic (same fertilized eggs, 100% genes in common), dizygotic (two separate feritilization events, share 50% of genes in common) Twin studies (measuring concordance) When a trait is exhibited by both twins: compare degree of concordance between monozygotic and dizygotic twins for given traits. If hereditary component is large, the mz twins should have larger concordance than dz twins The Leptin pathway and obesity Mutated ob genes in mice (ob/ob), gene encodes leptin hormone Leptin pathway=produced in fat cells (adipocytes), released by it, brain – bind receptors (hypothalamus), brain responded by releasing appetite-suppressor, increase in metabolic rate
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genomeguide2 - random genome study guides

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