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Characterization and evolution of ovine MHC class II DQB sequence polymorphism
R A van Oorschot1, J F Maddox, L J Adams
1State Forensic Science Laboratory, Macleod, Australia.
Animal Genetics
|December 1, 1994
Summary
Researchers characterized 10 novel ovine DQB exon 2 sequences in merino sheep, revealing high genetic diversity. This polymorphism suggests ancient DQB gene lineages predating species divergence.
Area of Science:
- * Molecular genetics
- * Immunogenetics
- * Comparative genomics
Background:
- * The Ovine Leukocyte Antigen (OLA) complex plays a crucial role in immune response.
- * Understanding DQB gene polymorphism is vital for sheep breeding and disease resistance.
Purpose of the Study:
- * To sequence and characterize the second exons of OLA-DQB genes in merino sheep.
- * To assess the polymorphism within the OLA-DQB region.
- * To investigate the evolutionary history of DQB gene lineages.
Main Methods:
- * DNA sequencing of OLA-DQB second exons from 13 merino sheep.
- * Polymerase chain reaction (PCR) amplification and cDNA library isolation.
- * Single-strand conformation polymorphism (SSCP) analysis for sequence discrimination.
Main Results:
- * Ten distinct OLA-DQB exon 2 sequences and corresponding amino acid sequences were identified.
- * The OLA-DQB region exhibits significant polymorphism: 29% nucleotide and 46% amino acid variation.
- * Evidence suggests at least two lineages of DQB genes, with some ovine sequences resembling bovine counterparts.
Conclusions:
- * The OLA-DQB region in merino sheep is highly polymorphic.
- * Ovine and bovine DQB gene lineages likely predate the species' separation over 20 million years ago.
- * SSCP is an effective method for discriminating OLA-DQB sequences.