EXTENSIVE CHROMOSOME BREAKAGE OCCURRING SPONTANEOUSLY IN A CERTAIN INDIVIDUAL OF ELYMUS FARCTUS. (=AGROPYRON JUNCEUM)
Bibliographic record
Abstract
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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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".