アブラナ カ ファストプランツ Brassica rapa ヘンイタイ ノ メンデル イデン ガクシュウ キョウザイ カ ニ カンス ル ケンキュウ

The two alleles of a gene Antocyaninless of FastPlants Brassica rapa were applied to learning of Mendel’s Law of Segregation as the biological teaching material in Japanese lower secondary school. Cross-hybridization was necessary because seeds can be generated only in cross-fertilization. First, P1, purple stem, and P2, nonpurple stem, were crossed each other. The only one plant was cultured in the pot. Only one pot of P1 was taken to University student’s home and cultured together with only one pot of P2 because cross-fertilization should be prohibited in the same strain, for example, P1 each other. The first cross should be performed between only P1 and P2. The F1 seeds, all of which showed purple phenotype, were cultured as a group of many pots because of the same genetic type of heterologous zygote, and then crossed each other. F2 seeds, twenty to twenty six, were cultured for 2-3 days on filter paper wetted with tap water in a Petri dish in water-supplied tray under luminescence light. The number of cultured F2 seed was approximately 500. The three phenotypes, concentrated purple, light purple, and green, were separated as the expression of genotypes of dominant homozygote, heterozygote, and recessive homozygote, respectively. As the results, the phenotype ratio of purple to non-purple was separated into 3 : 1. The expression of genotypes of dominant homozygote, heterozygote, and recessive homozygote, could be also divided into 1 : 2 : 1. The χ-squared test approved the separation ratio in 5%. The period of three months and a half was needed, however, it was suggested that the cross experiment can be carried out in spring to summer or autumn even in lower secondary school. ファストプランツのアントシアニンレス遺伝子に注目し，その優性と劣性の二つの対立遺伝子を中学校理 科メンデル遺伝における分離の法則の観察実験に応用するためのプロトコルを作成した。ファストプランツ は他家受粉で結実する。P1 のパープルステムとP2 のノンパープルステムを交雑する際は，各々の株をポッ トあたり一つ植えたP1 とP2 各々一つずつを学生の家に持ち帰らせ，開花・受粉させた。P1 同志やP2 同志 での交配が起こるとF2 での分離比に影響するからである。その結果，F1 は全て優性の形質を示した。F1 の 栽培は集団でまとめて行い，互いに交配させた。F2 の発芽は，水道水で湿らせたろ紙を置いたペトリ皿で2 日ほど発芽させた。このペトリ皿は水道水を張ったトレイに斜めに置いて給水を切らさないようにした。ペトリ皿あたり20 ～ 26 個，計500 個ほどのF2 を発芽させた。その後，濃い紫，薄い紫，緑の形質別に乾い たろ紙上に取り分け，各々の表現型の数を数えた。その結果，紫と緑の表現型は3：1 に，濃い紫，薄い紫 と緑，即ち優性ホモ接合体，ヘテロ接合体，劣性ホモ接合体の各遺伝子型は1：2：1 に分離していることが 確認され，これらの分離比は，危険率5％で有意な比と言えた