1.クローズド・コロニーとして維持されているマウス集団に育種学的操作を加えようとする時は集団遺伝学的な理論を応用せねばならない。この場合集団遺伝学の理論的展開をおこなう上での重要なパラメーターの1つである集団の有効な大きさを推定する必要がある。
2.一般の家畜の集団に適用する目的をもって導びかれた集団の有効な大きさ (N) の推定式にマウス集団でみられる繁殖構造上の特性を導入し, 以下に示す式を導びいた。この式において, sは親世代から仔世代への増減率を, Cは1匹の雄親に交配されている雌親の数を, Nmは親世代で繁殖に使用されている雄親の個体数を, σ²kmは雄親が仔世代へ寄与した仔 (配偶子) の数の分散を示している。
3.実験動物中央研究所で維持されているICR-JCL集団を用いて調査をおこない, 上記の推定式を導びくために必要な条件がほぼ満足されていることを示した。
4.更に上記のICR-JCL集団について, 5世代にわたり有効な大きさを推定した結果1世代当り300～400の間であることが判明した。また, この集団の見かけの大きさと, 有効な大きさが, いちじるしく異なる原因は, 雌雄の個体数が異なることと, 各個体の残した仔数の分散が, ランダムに残した場合の分散に比して異常に大きいことによるものであることを論じた。
本研究をおこなうに当り, 終始御指導, 御助言を賜った名古屋大学農学部野沢謙助教授ならびに近藤恭司教授に厚く御礼申し上げる。また, いつも変らぬ御鞭撻と有益な御批判をいただく東京大学医科学研究所田嶋嘉雄教授ならびに実験動物中央研究所長野村達次博士に謝意を表する。

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Loaches, Misgurnus anguillicaudatus, collected from Torentsu river, Ibaraki, Japan, were found to comprise two types based on the morphological and genetic traits. Complete substitution of alleles of the two types at the AAT-2* and GPI-1* loci were found, as well as significant differences in allele frequencies at eight other loci. The genetic distance between the two types was 0.4. The belly color was yellowish in type I and grayish in type II, and the average number of precurrent rays was 21.4 (range: 16-25) and 10.5 (range: 7-13), respectively.
The results suggested that the two types should be regarded as a distinct biological species.

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南米シャーガス病の主要伝播種であるサシガメTriatoma infestansの染色体(2n=20+XY, XX)をC-バンド分析したところ, 少なくとも3種(A, B, およびC)の多型が観察された。B型は, AおよびC型の雑種による異型接合体であることが判明した。そこで, この多型を指標として, 実験室内で任意交配の可能な状況で飼育されているブラジル株コロニーを集団遺伝学的に分析した。その結果は, この集団が非であり, 何らかの生殖的障害あるいは不和合性などにより, 多型間の任意交配が妨げられている可能性を示唆した。このC-バンド多型は, T. infestansの防圧計画のさいに重要な指標となると期待される。

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A genetic analysis of wild-caught tetsugyo from Yutori-numa Pond, Miyagi Prefecture, a long-finned fish of uncertain origin designated as a National Natural Monument in Japan, demonstrated that some specimens were hybrids of goldfish (Carassius auratus) and crucian carp (genus Carassius). Phylogenetic analysis of sequences from part of the D-loop region of mitochondrial and nuclear DNA of 87 Yutori-numa tetsugyo indicated that 66 belonged to the goldfish group and 21 to the Japanese crucian carp group, subsequent PCR-RFLP analysis of c-myc gene revealing three different restriction fragment digest profiles, 21 and 60 specimens possessing goldfish or Japanese crucian carp genes, respectively, and the remaining 6, both genes, indicating their hybrid origin.

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テンサイの一代雑種においては根重や糖量などの収量形質には，高いヘテロシス効果が認められる．ヘテロシス効果がどの程度交配に用いられる親系統間の近縁関係に依存するかを明らかにする目的で，5種類の雄性不稔系統とそれぞれの維持系統との間の片側ダイアレル交配15組合せの母本を準備し，共通の花粉親を交配した．得られた一代雑種を供試し,収量形質と交配親系統間の近縁係数の関係を解析した．また，北農研で育成された計1039の交配組合せについて育成系譜のデータベースを構築し，親系統間の近縁係数とヘテロシス効果との関係を解析した．一代雑種を構成する親系統間の近縁係数と糖量の相関関係は極めて高く，近縁係数が増大するに従い，ほぼ直線的に糖量が低下した．親系統間の近縁係数が0.1を超える交配組合せでは，糖量が標準品種「モノホマレ」を超えるものはなかった．わが国において1993年から2004年の11年間に生産力検定が行われた単交配F₁ 424組合せおよび三系交配F₁ 250組合せの交配に用いられた親系統間で，糖量と近縁係数との関係を調査した．その結果，近縁係数が0.1を越える交配組合せにおいては，「モノホマレ」以上の糖量を示した組合せは少なく，糖量の多い交配組合せは親系統間の近縁係数が0.1以下の交配組合せが大半であった．よって，テンサイの一代雑種品種育成では，親間の近縁係数が0.1以下となる交配組合せを選ぶことにより，ヘテロシス効果を効率的に利用できることが明らかとなった．

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Genetic divergence between non-scaly form and scaly form of pen shell Atrina pectinata (Linne) was examined. Isozyme analyses indicated replacement of major alleles at the AAT^*, CK-1^*, GPI-1^*, GPI-2^*, LAP^*, MDH^*, MPI^* and PGM^* loci, and difference of allele frequency at the GAPDH^* loci. Heterozygosity histogram of scaly form indicated a bimodal distribution, some individuals of the scaly form had many heterozygotes at the diagnostic loci. The obsevation that the shell morphology of the individuals showed intermediate state between non-scaly and scaly form suggested that they were hybrids between the two forms. The genetic distance (D value) between the two forms, calculated from isozymic allele frequencies, was 0.469, a figure significant at the inter-specific level. The considerable genetic difference and the presence of low frequency of hybrids in a sympatric population suggested that the two forms are distinct species. Morphologically, since the two forms could be completely distinguished by presence of the squamation, the two forms should be taxonomically distinguished.

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1. 実中研で維持•繁殖されているクローズド•コロニー群(ICR-JCL)マウスの繁殖構造を知り,維持方法を検討する目的で調査をおこなつた.
2. ICR繁殖集団の雄300匹,雌1,800匹について,次の世代で繁殖に使用された仔を残した親を調査したところ,雄は229匹(76.3%)が,雌は385匹(21.4%)が次世代に種仔マウスを残していることが判明した.
3. ICR繁殖集団の有効な大きさは約350で,ヘテロ性の失なわれる率は毎世代約0.14%である.
4. 2.5年間,5.8世代の近交係数の上昇は0.828%で,1世代当り0.143%である.また,Index of sub-dvisionは0,86で,近交回避の効果が現われている.
5. ICR-JCL繁殖群はクローズド•コロニー群として,育種学的に満足すべき状態で維持されていることが判明した.

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生物種の遺伝的構造は確率的要因によって決まることが多い. 中でも分子進化や蛋白質多型現象の遺伝学的理論では確率過程の理論は極めて重要な役割を演じている. 遺伝学のこれらの分野で要求される数学的モデルの多くは次元数の大きい空間の過程であること, 拡散項が非線形でしかも境界に特異点をもつことなどから, きれいな型で解を求めるのは不可能である. 一方, 伊藤型の確率積分を用いて数値的にシミュレーションすることは, 最近のコンピューターの進歩と相俟って容易になった. 今後一層必要となる数学的モデルの解析において確率積分はますます重要な方法となるであろう. このあたりの事情と問題点を幾つか紹介する.

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The paternity test may be necessary even on pasturing beef cattle in order to clarifythe pedigree of offspring, find out a bull carrying undesirable genes resulting in givingbirth to abnormal calves, and study tlte breeding behavior of bulls in pasture.In this investigation, the efficiency of various blood grouping systems for paternitycases involving two or more bulls was estimated from gene frequettcy data in JapaneseShorthorn cattle. The results actually obtained are shown below.(I) The expected probability of making exclusion for paternity cases involving twobulls by nine systems of red-cell antigens was 0.705, artd that by live protein types was0.490. It increased to 0.850, however, when estimated by the combined use of all tlaesystems.(2) In paternity cases involving more than two bulls, the probability of makingexclusion was calculated from the following formula: P.zP.Cn=1>, where P. is the prob-ability of exclusion in two bulls and n is the number of bulls involved. In pasturingJapanese Shorthorn cows with five bulls, the probability of making exclusion decreasedto 0.522.(3) In nineteen actual paternity cases in pasturing cattle, including three possiblebulls, about 84% of the cases were solved by all the systems combined.

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千葉¹⁾および福原²⁾はスギの園芸品種,ミドリスギの冬期間の緑色は1個の劣性遺伝子によることを報告した。放射線育種場の採穂園からのさし穂により育苗したスギの3品種,メアサ,キリシマメアサおよびアオスギを自殖し,または,ミドリスギの劣性遺伝子をホモ型でもっ2個体(ミドリスギ(5)およびGR)と交配した。自殖の結果,苗の冬期聞の色彩についての分離は,アカ:ミドリが, 3:1であり,また,他殖の結果,アカ:ミドリの割合は, 1:1であることが証明された。このため,これらの品種の中には同一のミドリスギの劣性遺伝子をヘテロでもつ個体が存在するものと思われる。

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The samples from 6 natural populations of amphidromous race collected in Kochi Prefecture, 2 from landlocked populations, and 2 artificially propagated populations of Ayu, Plecoglossus altivelis were used for examining isozyme markers in order to clarify genic variability and differentiation of populations. Among 20 loci examined, 14 loci were polymorphic in total samples. The genic variability was not low in comparsion with the other fish species, as shown in the number of alleles per locus ranging from 1.25 to 1.60, the proportion of polymorphic loci per population from 0.250 to 0.450, and heterozygosity from 0.034 to 0.090. The level of genic variability of landlocked form was lower than the amphidromous form. The allele frequency was very similar within a race as shown by the genetic distance (D=0.0001-0.0008 in amphidromous form, D=0.0003 in landlocked form). On the other hand, the genetic distance between amphidromous and landlocked forms was relatively large (D=0.0035). Distinct change was observed in the allele frequencies and genic variability in the hatchery population, possible effects of founder population and selection being suggested.

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Thirteen isozymes of various organs and sarcoplasmic protein of muscle of the red sea bream, Pagrus major (Temminck et Schlegel), were assayed by the horizontal starch-gel electro-phoresis in order to detect the genetic variation which would be useful as the maker in subpopulation and breeding studies. Polymorphism was found in various isozyme systems such as ADH, esterase, α-GDH, GOT, ICD, LDH, MDH, 6-PGD, PGM, PHI, and SDH. Based on the polymorphic banding pattern of each isozyme, two alleles were presumed in the respective loci, such as α-Gdh, Got-III, Icd, Ldh-B, Pgm, and Sdh, three alleles in Adh, Got-II, Mdh, 6-Pgd, and Phi-II loci, and 8 alleles in Est locus. There were no significant differences between observed proportion of phenotypes and their H_ARDY-W_EINBERG expectation in most of the loci examined. The proportion of polymorphic loci was 34.3%, a relatively high value in comparison with other marine fishes. The proportion of occurrence of Heterozygous loci per individual was 6.6%, a comparatively similar rate to other marine fishes. The growth rate of wild red sea bream at 1 year old was independent of polymorphism in each enzyme system. It was concluded that the ADH, EST, 6-PGD, PGM, and SDH isozymes would be useful as characteristics of subpopulation and as genetic markers of the family and brother-sister in breeding studies.

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To clarify the taxonomic status of two forms (Awajichihiro and Yaminonishiki) of Hirase's scallop Volachlamys hirasei, genetic characters by isozyme analysis were examined as the fourth report of series studies. Since fitness for Hardy-Weinberg equilibrium by chi-square tests indicated no significance at any polymorphic loci in Awajichihiro form, Yaminonishiki form and both the forms pooled, no evidence that the two forms were distinct reproductive populations was recognized. Also, there were no significant differences between the two forms in the values to indicate genetic features and allelic frequencies of the 24 loci examined. The genetic distance (D value) between the two forms indicated 0.0002, being in the level below inter-local population or the same species. The results strongly suggested that the Awajichihiro and the Yaminonishiki forms belong to a single reproductive population, namely the same species, and the morphological variabilities are regarded as phenotypes of the genetic polymorphism. The taxonomic status was decided as follows : Hirase's scallop (Awajichihiro-gai) Volachlamys hirasei (Bavay, 1904) Awajichihiro form V. hirasei var. awajiensis Yaminonishiki form V. hirasei var. ecostata

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