Investigation of the major gene presence responsible for egg weight in chicken, with dealer segregation analysis

Segregation analysis is a method that predicts monogenic and polygenic elements with statistical models and detects major genes. The main purpose of this study is; it is the investigation of whether egg weight is driven by a major gene or not by using bayesian segregation analysis using a data set of a chicken population. For this purpose, a pre-collected data set was used, using the egg weight (first egg weight, 36., 56., 66., 72., 80. weeks egg weight) and pedigree information for a total of 7 time periods from 1063 laying hen lines, and the presence of major genes examined. Variance components were estimated by Gibbs sampling. In this study, additive genetic variance, error variance, major gene variance, additive and dominant gene effects were estimated by segregation analysis. According to the analyzes performed, it was found that the dominant effect (-7.30, 0.66, -2.42, -18.57, -2.94, -5.83, -2.54) on egg weight was smaller than the additive gene effect (11.79, 2.00, 3.38, 9.07, 4.53, 5.67, 5.49). . Major gene variances (σ2G = 53.34, 3.33, 8.24, 60.24, 11.14, 17.72, 28.23) were found to be greater than the polygenic variance (σu2 = 6.53, 5.68, 2.38, 6.52, 7.28, 6.11, 4.69). Major gene frequency for 7 time periods, p = 0.86 and q = 1- p = 0.14, p = 0.58 and q = 1 - p = 0.42, p = 0.53 and q = 1 - p = 0.47, p = 0.84 and q = 1 - p = 0.16, p = 0.73 and q = 1 - p = 0.27, p = 0.63 and q = 1 - p = 0.37, p = 0.64 and q = 1 - p = 0.36. Three different analyzes were conducted: 1) weekly egg weights 2) exponential growth model analysis 3) principal component analysis. In major gene analysis, in the polygenic model, the h2 = 0.31 (± 0.54), 0.51 (± 0.56), 0.54 (± 0.56), 0.32 (± 0.52), 0.44 (± 0.54), 0.27 (± 0.50), 0.25 (± 0.51), and the degrees of inheritance in the major gene model h2 = 0.81 (± 0.94), 0.67 (± 0.81), 0.95 (± 0.88), 0.85 (± 0.98), 0.70 (± 0.85), 0.70 (± 0.90), 0.73 (± 0.95) In the polygenic model; h2 = 0.99 (± 0.91), 0.46 (± 0.54), 0.85 (± 0.60), 0.87 (± 0.61), 0.92 (± 0.60), 0.79 (± 0.59), 0.96 (± 0.66) and in major gene model analysis; Finding h2= 0.80 (± 0.95), 0.54 (± 0.64), 0.60 (± 0.27), 0.56 (± 0.81), 0.75 (± 0.88), 0.72 (± 0.94), 0.76 (± 0.94) polygenic h2 = 0.63 (± 0.57), 0.15 (± 0.09), 0.12 (± 0.47) for the model, and h2 = 0.71 (± 0.73), 0.20 (± 0.70), 0.50 (± 0.93) in the major gene model. There was no similarity between heritability levels in these different analysis types. However, determining the high heritability levels for the polygenic model in all three methods shows that egg weights can be used successfully in time-based selection studies.