IgY is the homologue of immunoglobulin G in mammals and is composed of four polypeptide chains (two light and two heavy chains). The IgY light chain has 2 domains (variable and constant) in chickens. The constant regions possess class and subclass markers of the immunoglobulin and the variables region is involved in antigen recognition and binding. The aim of this research was to reveal the genetic and phylogenetic analysis of the light chain of immunoglobulin Y transcripts in Khorasan native chickens. For this purpose, 20 spleen samples were collected from the chickens for RNA extraction and cDNA synthesis. The IgY light chain with a length of 764 bp was amplified by polymerase chain reaction using specific primers. After sequencing, mutation investigation was performed in the constant and variable regions. The results demonstrated that CDR3 and constant regions had the highest variation. Phylogenetic analysis showed that the coding gene of IgY in Khorasan native chickens had the highest similarity with French leghorn and United kingdom chickens. The constant region possessed four alpha helix structures compared to the variable region which had no alpha helix structure according to amino acid sequencing analysis and active site determination. Altogether, this study demonstrated for the first time the phylogenic basis of genetic diversity in Khorasan native chickens.

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