EXTENSIVE CHROMOSOME BREAKAGE OCCURRING SPONTANEOUSLY IN A CERTAIN INDIVIDUAL OF ELYMUS FARCTUS. (=AGROPYRON JUNCEUM)
Notice bibliographique
Résumé
PONTANEOUS chromosome breakage has been reported frequently S in the literature.In the majority of those cases when breakage is unusually high, the effect is confined to a certain kind of tissue or a special type of cells, sometimes only to a certain stage of development.The ordinary frequency of spontaneous breaks is, in general, low.The present paper is devoted to a study on spontaneous chromosome breakage in one individual of the grass Elymus farctus ssp.boreo-atlanticus (= Agropyron junceum ssp.boreo-atlanticum; RUNEMARK and HENEEN, 1963).In this special individual, chromosome breakage is unusually frequent in mitotic as well as meiotic cell divisions.Spontaneous chromosome breakage during meiosis was reported in a variety of materials by many workers.Cases were described, e.g., by REES (1952 a and b) in Scilla, MARQUARDT (1952) and WALTERS (1956) in Paeonia, HAGA (1953) in Paris and NEWMAN (1959) in Podophyllum.Intensive breakage was found at meiosis in certain interspecific and intergeneric hybrids, e.g., by WALTERS (1950, 1952, 1955 and 1957) in Bromus, and by HENEEN (1963 a and b) in an ElymusXSecale hybrid and in Elymus.In Tradescantia (GILES, 1940, 1941), and Tulipa and Hyacinthus ( DARLINGTON and UPCOTT, 194 1) , spontaneous breakage was detected at pollen grain mitosis.In certain species and hybrids breakage was observed in endosperm as described by CLARK and COPE-LAND (1940) for Zea, BROCK (1954, 1955) for Lilium and Hyacinthus, RUTISHAUSER (1956) for Trillium and RUTISHAUSER and LA COUR 1 -Heredifas 49 2 WAHEEB K. HENEEN (1956) for the intergeneric hybrid TrilliumXParis.In most of the materials mentioned above, the spontaneous chromosome breakage was thought to be caused by a disturbance in the genetic balance.A number of workers reported spontaneous breakage from somatic tissues of root tips: Studies by NAVASHIN (1931) on Crepis; NICHOLS (1941), KATO (1954) and SAX and SAX (1961) on Allium; LEVAN and LOTFY (1950) and SHARMA and BHATTACHARYYA (1956) on Vicia; D'AMATO (1948, 1951) on Nothoscordum and Pisum; KATO (1955, 1960) on Lilium and Cliuia; RILEY and HOFF (1958) on Tulbaghia; THOMAS (1960) on Chlorophytum; and ISING (1962) on Cyrtanthus.Most of these authors, in interpreting the phenomenon of spontaneous chromosome breakage, stressed the possibility of an automutagenic effect of certain metabolites produced in the plant itself.In some of these species, the frequency of chromosome breakage was studied in relation to the different developmental stages of the seedlings and to seed age.Spontaneous breakage also was recorded from the somatic tissues of the young leaf meristem in Ginko (TANAKA et al., 1952), and from the cotyledons of Pinus (TJIO and ~S T E R G R E N , 1954).Furthermore, aberrations and irregularities were found in malignant cell lines (e.g., LEVAN and BIESELE, 1958).Chromosome breakage can be induced experimentally by various mutagenic agents such as radiation and chemicals (SAX, 1957; KOLLER, 1954; SHARMA and SHARMA, 1960; KIHLMAN, 1961).Extensive work done in this field by many authors furnished considerable information about the phenomena of chromosome breakage.According to these studies the aberrations can be classified into either chromosome or chromatid types, depending on whether the breaks and subsequent unions occur before or after the effective splitting of the chromosome.Both types of aberrations involve deletions and exchanges.Most of the types of aberrations obtained with mutagenic agents occur naturally in the material to be discussed here. MATERIAL A N D METHODSDuring a study by HENEEN (1962 b) on the karyotype of Elymus farctus ssp.boreo-atlanticus ( = Agropyron junceum ssp.boreo-atlanticum), one individual plant was found to show an abnormally high frequency of spontaneous chromosome breakage.This plant is one of four individuals raised in 1957 from seeds collected in 1956 by Dr. G.
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Comment cette classification a été obtenuedéplier
Prédiction machine sur la base complète
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Scores du classifieur distillé par catégorie (deux têtes)
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,000 | 0,000 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,001 | 0,000 |
| Études des sciences et des technologies | 0,000 | 0,000 |
| Communication savante | 0,000 | 0,000 |
| Science ouverte | 0,000 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,001 | 0,000 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule source (Gemma direct ou Codex distillé), pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».