MHC diversity arises from:

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(No Transcript)
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MHC diversity arises from

• Polygenicity
• Polymorphism
• Co-dominance
• Linkage disequilibrium

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Polygenicity
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

• 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
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Co-dominance

• Full expression in the heterozygous state

• Linkage disequilibrium
• 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
  ?nr519

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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.)

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Haplotype

• Think Polygenicity, polymorphism,
  co-dominance, and linkage disequilibrium.

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Haplotype

• Think Polygenicity, polymorphism,
  co-dominance, and linkage disequilibrium.

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Genetic organization in the mouse is similar
continue to think about polygenicity,
polymorphism, co-dominance, and linkage
disequilibrium
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And, the result is
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So

• thats the genetics
• what does the synthesis of the protein look like?

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Classical and non-classical MHCs

• Classical are expressed continuously.
• Non-classical are expressed in specific tissues
  and/or at specific times.

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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?)

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MHC- III

• Complement
• Tumor necrosis factor
• Heat shock proteins
• Hydroxylases
• (generally) genes related to inflammation