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MHC diversity arises from:

MHC diversity arises from:. Polygenicity Polymorphism Co-dominance Linkage dis equilibrium. n [ ISV ] (1941) : possessing any of a group of nonallelic genes that collectively control the inheritance of a quantitative character or modify the expression of a quantitative character.

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MHC diversity arises from:

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  1. MHC diversity arises from: • Polygenicity • Polymorphism • Co-dominance • Linkage disequilibrium

  2. n [ISV] (1941) : possessing any of a group of nonallelic genes that collectively control the inheritance of a quantitative character or modify the expression of a quantitative character Polygenicity: Polymorphism: n [ISV] (1839) : the quality or state of being able to assume different forms: as a : existence of a species in several forms And by extension: existence of a gene in several forms

  3. Co-dominance: • Full expression in the heterozygous state • Linkagedisequilibrium: • When the observed frequencies of haplotypes in a population does not agree with haplotype frequencies predicted by multiplying together the frequency of individual genetic markers in each haplotype. • http://hal.weihenstephan.de/genglos/asp/genreq.asp?nr=519

  4. MHC haplotypes are in disequilibrium: Two explanations are offered: • There has not been enough “evolutionary” time to achieve equilibrium • Some allelic sequences in the haplotype are adaptive (i.e., they are suited to displaying frequently occurring “foreign” peptides.)

  5. Haplotype: • Think “Polygenicity,” “polymorphism,” “co-dominance,” and “linkage disequilibrium”….

  6. Haplotype: • Think “Polygenicity,” “polymorphism,” “co-dominance,” and “linkage disequilibrium”….

  7. Genetic organization in the mouse is similar… continue to think about polygenicity, polymorphism, co-dominance, and linkage disequilibrium

  8. And, the result is:

  9. So… that’s the genetics… what does the synthesis of theprotein look like?

  10. “Classical” and “non-classical” MHC’s “Classical” are expressed continuously. “Non-classical” are expressed in specific tissues and/or at specific times.

  11. Linkage disequilibrium (again) Some haplotypes correlate with increased incidence of disease. Such association is measured by a “relative risk” factor (RR). (Ag+/Ag-) disease RR = _____________________ (Ag+/Ag-) control Question: to what does “Ag+” refer?)

  12. MHC- III • Complement • Tumor necrosis factor • Heat shock proteins • Hydroxylases • (generally) genes related to inflammation

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