The insulin-like growth factor, IGF-I, plays an important role in the development of growth and reproductive traits. Singlestrand conformation polymorphism analysis was used to detect and analyze polymorphisms and expression profiles of the IGF-I gene and its association with growth and reproductive traits of Jinghai yellow chickens. A point mutation g.295T>C was detected in the IGF-I gene with three genotypes CC, CT, and TT. The CT and TT genotypes were found to be significantly (P < 0.05)

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... rior to the CC genotype in 8-, 10-, 12-, 14-, and 16-week-age weight of chickens (for growth traits) and in body weight at first egg-laying (for reproductive traits). Comparison of the expression level between males and females showed similarity in their expression curves, with females showing relatively higher IGF-I expression than males in all studied tissues. A similar IGF-I expression pattern was observed in the breast and leg muscles of both males and females, with the leg muscle showing relative higher IGF-I expression than the breast muscle. Our results indicate that, g.295T>C mutation in the IGF-I gene affects certain growth and reproductive traits, and it could be used to provide a theoretical basis as well as marker-assisted selection to upgrade the development of Jinghai yellow chickens in future.