Evidence of genotypic variation, MHC class I copy number variation and recombination within the chicken major histocompatibility complex-y system
Kopulos, Renee T.
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The major histocompatibility complex (MHC) is a gene region found in all jawed vertebrates. These highly polymorphic, tightly linked genes are responsible for immune regulation by presenting self and non-self antigens to the immune system. The MHC is the most polymorphic vertebrate genome region because its genes face considerable selective pressure since survival depends on the capacity to respond to bacterial, viral and parasitic diseases. The MHC organization in different species has clearly evolved in separate and unique ways since the time that birds and mammals diverged from a common ancestor 310 million years ago. The size and organization of chicken MHC genes is somewhat different from the MHC regions found in mice and humans. Given the wide variability in gene numbers revealed in this study, I wanted to determine whether genetic recombination, crossing over, in the MHC-Y region might be contributing to haplotypic variation. YF molecules seem to have a high recombination frequency between its multiple copies, perhaps on the order of 1% (1 map unit) or higher. This may be due to many similar genes present within the MHC-Y region. Proximity of a 41 base pair repeat known as PO41 might also contribute to instability of the region.