ISSN:
1432-0886
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Medicine
Notes:
Summary 1. Reciprocal crosses were carried out between representatives of the group of Eu-Oenothera on the one hand and those of groups Raimanniaor Renneria-Oenothera, resp., on the other, in order to homologize the numeration of their chromosome ends. The crossings were often unsuccessful, especially when the Eu-Oenothera were functioning as female plants. It appears that the constitution of the plastome is frequently responsible for the death of the hybrids. 2. The diakinesis configurations of the chromosomes typical for each hybrid were determined as far as this was possible. The investigations were rendered extremely difficult by the high rate of missing connections in the chromosome rings and chains. The typical configurations could only rarely be observed but rather had to be derived from comparisons of torn chromosomal chains. The typical configurations as determined consist mostly of many-membered rings. 12°+2°, 10°+2°+2°, 10°+4° and 14° are by far the most frequent. 3. In some types of the hybrids other configurations occurred in addition to the characteristic configuration, which, however, could not be reconciled with their characteristic one. In most instances certain deviating chromosomal configurations were preferably observed. Even trivalent connections occurred in these forms, which are not expected in the normal Oenotherae with 14 chromosomes. 4. Point (2) and (3) are obviously the result of the distant genetic relationship between the partners of the crossing. This reduces the formation of chiasmata because of a lower intensity of pairing, which again leads to an increased failure to end connections. Furthermore, the pairing of non-homologous chromosomes is increased (trivalent connections!) which may lead to translocations resulting in deviations from the typical configuration. These frequently occurring deviations in configuration make it probable that short homologous segments do exist in the pairing chromosomes which are strictly speaking non-homologous. The rate of translocations in Oenothera is apparently determined to a large extent by endogenous genetic factors. This assumption is supported by other findings.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00332609
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