Parenting by persons with intellectual disability: an explorative study in the Netherlands.

BACKGROUND: As a sequel to a report by the Health Council of the Netherlands on contraception in persons with intellectual disabilities (IDs), a fierce debate about parenthood by such persons occurred, in which a lack of knowledge about parenting competences became clear. Therefore, the Ministry of Health commissioned a study investigating examples of 'successful parenthood' by persons with IDs. METHODS: In conformity with the literature and with legal categories, we defined 'successful parenthood' as 'good enough parenthood', meaning no indications for child abuse and/or neglect, no dealings with child protection agencies and no legal custody. We combined a nationwide quantitative questionnaire study with a qualitative interview study. Questionnaires were sent to all institutions involved in caring for persons with ID, interviews were held with 'good enough' parents and their professional caregivers, selected on the basis of returned questionnaires. RESULTS: Parenthood occurs in around 1.5% of persons with ID in the Netherlands and is mostly restricted to those with mild handicaps. In total, 51% of the cases were regarded, by caregivers, as not-good-enough parenthood, 33% were clearly good enough and 16% were doubtful. Predicting factors included the ability and the willingness to follow advice, the quality of the social network and the acceptance of parenting in the community. However, there is not one decisive predicting factor; particularly, the predictive value of the IQ alone is small. CONCLUSIONS: A general policy of discouragement of parenthood, as advocated by the Dutch Ministry, is not supported by our results; moreover, it would probably be impossible and have negative effects on social acceptance of parents with ID. The overall conclusion from the study therefore is that some kind of balancing model, in which positive and negative factors are weighed, may be useful to predict success and need for support.

Giemsa G-banding in Allium.

Using divergent Giemsa staining protocols designed for other plant species, G-banding was visualized in the chromosomes of Allium cepa L., A. fistulosum L., and their interspecific (A. fistulosum x A. cepa) hybrid. This is the first demonstration of G-banding of Allium chromosomes. Differences and similarities with other Giemsa banding patterns in Allium are discussed.

Meiotic behaviour of telo-tertiary compensating trisomics of rye: evaluation for use in hybrid varieties.

Meiosis of four telocentric-tertiary compensating trisomics of rye (Secale cereale L.) was studied with the purpose of evaluating their suitability for use in maintaining genic male-sterile lines applied in hybrid varieties. They had been constructed from four different reciprocal translocations and three different telocentrics. In one trisomic a slight, but significant tendency was demonstrated for preferential pairing of the two normal chromosomes associated with the compensating complex. This promotes the desired segregation into one normal and one compensating karyotype. In all trisomies, however, too high a frequency of failure of chiasma formation in a critical segment of the complex was evident. This is correlated with the ease of recovery of the trisomics, but results in undesired segregational products. Interstitial chiasmata leading to the formation of branched configurations were also present, more in some trisomics than in others. These also result in undesired segregations. The behaviour at meiosis was so closely correlated with the length of the chromosome segments involved that a prediction of the most favourable combination of telocentric and translocation can be made. The telocentric should be large, the corresponding translocated segment large and the interstitial segment small. The non-translocated arm of the translocated chromosome should be large and the second translocated segment small. The combinations of translocations and telocentrics had not been selected for these criteria and did not meet the requirements for practical application.

High recombination between the breakpoint of a reciprocal translocation in rye (Secale cereale L.) and an interstitially located gene.

The recombination fraction between the interstitially located gene an and interchange 303 of rye was found to be 0.244±0.038 in a test cross using the translocation as the male parent. In first metaphase translocation configurations in pollen mother cells of the same plant, the chiasma frequency between an and the translocation breakpoint was found to be significantly more than twice the recombination fraction. Recombination was concluded to be masked by a difference in the alternate frequency between configurations without interstitial chiasmata and configurations with interstitial chiasmata, the effect of the first type being of major importance. Random centromere orientation of translocation multivalents with interstitial chiasmata was concluded to be a realistic assumption. The exceptionally high recombination between an and translocation 303 is discussed. Consideration is also given to the use of interchanges in the establishment of a marker's chromosomal position, and to the use of translocation chromosomes in balanced systems for hybrid breeding purposes.