Genetic gain - genetic gain

…Heritability is estimated by variance analysis from parent-child correlation and measurements of several pairs of siblings. For example, it has been reported that the heritability of egg weight for White Leghorn chickens is 0.6, the age at which eggs first lay is 0.5, and body weight is 0.2. Once the heritability is known, the degree of improvement in the average value that can be expected from selection in one generation when breeding is performed through selection (called the genetic gain) is expressed as the product ⊿ G = ih ² of the selection difference i (the difference between the original average and the average of the selected individuals taken to create the next generation) calculated from the strength of this h 2 ^selection . If the genetic composition does not change suddenly due to selection, we can expect that much improvement in each generation, but in reality, good genes are fixed and the genetic variance decreases, resulting in a decrease in heritability, and if selection is continued for a long time, it will reach a plateau. …

*Some of the terminology that refers to "genetic gain" is listed below.

Source | Heibonsha World Encyclopedia 2nd Edition | Information

…遺伝率は親子の相関や幾組もの兄弟の測定値から分散分析を用いて推定されるもので，例えばニワトリの白色レグホーンで卵重の遺伝率は0.6，卵を産み初めの年齢は0.5，体重は0.2という報告がある。遺伝率がわかると，選抜により品種改良を行ったとき1世代の選抜で期待できる平均値の改良度合⊿G(これを遺伝的獲得量という)はこのh²選抜の強さから計算される選抜差i(もとの平均と次代を作るため取り出した選抜個体の平均との差)との積⊿G＝ih²で表される。選抜により遺伝的組成が急激に変わらないならば，毎代それだけの改良が期待できるが，実際には良い遺伝子が固定し，遺伝的な分散が減少する結果遺伝率も低下し，選抜を長く続けると頭打ちになる。…

※「遺伝的獲得量」について言及している用語解説の一部を掲載しています。

出典｜株式会社平凡社世界大百科事典 第２版について | 情報