초파리의 走光性行動에 대한 人爲淘汰와 自然淘汰

Artificial and Natural Selection for Phototactic Behavior in Drosophila melanogaster

1974年 安養에서 採集한 초파리의 走光性行動에 대한 人爲淘汰實驗을 행하였다. 淘汰의 結果, 第10世代까지의 走光性 및 避光系統의 遺傳率은 每世代當 2$\\sim$4%로 나타났다. 淘汰系統間의 相對交配實驗의 結果, 避光行動을 나타내는 遺傳子가 走光性遺傳子에 대하여 部分的 優性의 효과가 있음을 알았고, 그 효과는 淘汰의 後期世代에서 더욱 뚜렷하였다. 淘汰15世代後, 走光性과 避光性系統에 대하여 人爲淘汰를 中止하고 自然淘汰에 의한 遺傳子의 行動을 調査하였다. 實驗結果, 數世代以內에 最初集團의 走光性指數로 환원되었다. 이러한 현상은 自然淘汰에 의한 遺傳的復元性의 一例라고 생각된다.

Several hundred flies of Drosophila melanogaster collected in Anyang City were selected for positive, negative and neutral directions during 15 generations. The population responded effectively to the artificial selection. The realized heritability estimated for the first 10 generations was $2 \\sim 4%$ per generation in the positive and negative phototaxis. The results of diallel crosses among selected populations indicated that some polygenes showing a negative phototaxis were partially dominant over polygenes controlled the positive phototaxis, and the dominant effect became greater in later generations. The populations selected for positive and negative phototaxis were relaxed after 15 generations of selection, and their phototactic responses were completely returned to their original states. Such phenomena would be explained by the genetic homeostasis resulted from an action of natural selection. It seems reasonable to assume that the phototactic neutrality of a natural population was maintained as an adaptive trait under natural environment.