Studies on the Effects of Deleterious Genes on the Strains Selected for Photoaxis in Drosophila melanogaster

초파리에 있어서 주광성행동의 선발에 관한 유해유전자의 영향

The experiment has been analyzed for genetic architecture of behavioral trait in strains selected for positive and negative phototaxis in Drosophila melanogaster. Response to selection for two different directions was rapidly diverged in their phototactic scores. Realized heritabilities for the first teh generations of selection in the positive and negative strains calculated to be 3.08% and 2.86%, respectively in both sexes. The frequency of deleterious chromosomes(lethal and semilethal chromosomes) in the positively selected strain(43%) was higher than that of negatively selected one (18%). The unselected strain(27%) was intermediate frequency between both selected strains. The correlated relationship between deleterious genes and photopositive polygenes was confirmed by the phototactic behavior of the lethal heterozygotes($1_i/1_j$). Form the results, the deleterious genes induced by long term selection for phototaxis would be considered some linkage relationship with photopositive polygenes.

Multiple-unit classification maze를 使用하여 走光性行動에 關한 positive와 negative의 directional selection을 15世代동안 행하였다. 方向性 選拔에 의해 얻어진 兩系統의 遺傳的 構造를 알기위해 第2 染色體上에 위치한 致死遺傳子의 頻度를 調査하고 이들 有害遺傳子와 走光性行動과의 相關關係를 考察했다. 走光性에 對한 positive와 negative의 選拔 果는 初期부터 反應이 나타나 選拔後 第10世代동안의 realized heritaability는 positiver系統과 negative 系統이 각각 3.08%와 2.86%로 算定되었다. 第2 染色體의 有害遺傳子(lethal and semi-lethal)는 positive(43%)系統이 negative(18%)系統보다 훨씬 높은 빈도였다. 한편 無選拔 系統(27%)은 兩選拔 系統의 중간빈도였다. positive 走光性 遺傳子와 有害遺傳子의 相關關係는 각 選拔系統에서 축출한 2量 劣性 致死遺傳子($1_i/1_j$)에서도 확인하였다. 본 實驗의 결과로 走光性行動의 選拔에 의해 얻어진 positive polygene과 有害遺傳子 polygene과에 어떤 linkage의 相關關係가 존재한다고 사료된다.